/*
 * Virtio Support
 *
 * Copyright IBM, Corp. 2007
 *
 * Authors:
 *  Anthony Liguori   <aliguori@us.ibm.com>
 *
 * This work is licensed under the terms of the GNU GPL, version 2.  See
 * the COPYING file in the top-level directory.
 *
 */

#include "qemu/osdep.h"
#include "qapi/error.h"
#include "qapi/qmp/qdict.h"
#include "qapi/qapi-commands-virtio.h"
#include "qapi/qapi-commands-qom.h"
#include "qapi/qapi-visit-virtio.h"
#include "qapi/qmp/qjson.h"
#include "cpu.h"
#include "trace.h"
#include "qemu/error-report.h"
#include "qemu/log.h"
#include "qemu/main-loop.h"
#include "qemu/module.h"
#include "qom/object_interfaces.h"
#include "hw/virtio/virtio.h"
#include "migration/qemu-file-types.h"
#include "qemu/atomic.h"
#include "hw/virtio/virtio-bus.h"
#include "hw/qdev-properties.h"
#include "hw/virtio/virtio-access.h"
#include "sysemu/dma.h"
#include "sysemu/runstate.h"
#include "standard-headers/linux/virtio_ids.h"
#include "standard-headers/linux/vhost_types.h"
#include "standard-headers/linux/virtio_blk.h"
#include "standard-headers/linux/virtio_console.h"
#include "standard-headers/linux/virtio_gpu.h"
#include "standard-headers/linux/virtio_net.h"
#include "standard-headers/linux/virtio_scsi.h"
#include "standard-headers/linux/virtio_i2c.h"
#include "standard-headers/linux/virtio_balloon.h"
#include "standard-headers/linux/virtio_iommu.h"
#include "standard-headers/linux/virtio_mem.h"
#include "standard-headers/linux/virtio_vsock.h"
#include CONFIG_DEVICES

/* QAPI list of realized VirtIODevices */
static QTAILQ_HEAD(, VirtIODevice) virtio_list;

/*
 * Maximum size of virtio device config space
 */
#define VHOST_USER_MAX_CONFIG_SIZE 256

#define FEATURE_ENTRY(name, desc) (qmp_virtio_feature_map_t) \
    { .virtio_bit = name, .feature_desc = desc }

enum VhostUserProtocolFeature {
    VHOST_USER_PROTOCOL_F_MQ = 0,
    VHOST_USER_PROTOCOL_F_LOG_SHMFD = 1,
    VHOST_USER_PROTOCOL_F_RARP = 2,
    VHOST_USER_PROTOCOL_F_REPLY_ACK = 3,
    VHOST_USER_PROTOCOL_F_NET_MTU = 4,
    VHOST_USER_PROTOCOL_F_SLAVE_REQ = 5,
    VHOST_USER_PROTOCOL_F_CROSS_ENDIAN = 6,
    VHOST_USER_PROTOCOL_F_CRYPTO_SESSION = 7,
    VHOST_USER_PROTOCOL_F_PAGEFAULT = 8,
    VHOST_USER_PROTOCOL_F_CONFIG = 9,
    VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD = 10,
    VHOST_USER_PROTOCOL_F_HOST_NOTIFIER = 11,
    VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD = 12,
    VHOST_USER_PROTOCOL_F_RESET_DEVICE = 13,
    VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS = 14,
    VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS = 15,
    VHOST_USER_PROTOCOL_F_MAX
};

/* Virtio transport features mapping */
static qmp_virtio_feature_map_t virtio_transport_map[] = {
    /* Virtio device transport features */
#ifndef VIRTIO_CONFIG_NO_LEGACY
    FEATURE_ENTRY(VIRTIO_F_NOTIFY_ON_EMPTY, \
            "VIRTIO_F_NOTIFY_ON_EMPTY: Notify when device runs out of avail. "
            "descs. on VQ"),
    FEATURE_ENTRY(VIRTIO_F_ANY_LAYOUT, \
            "VIRTIO_F_ANY_LAYOUT: Device accepts arbitrary desc. layouts"),
#endif /* !VIRTIO_CONFIG_NO_LEGACY */
    FEATURE_ENTRY(VIRTIO_F_VERSION_1, \
            "VIRTIO_F_VERSION_1: Device compliant for v1 spec (legacy)"),
    FEATURE_ENTRY(VIRTIO_F_IOMMU_PLATFORM, \
            "VIRTIO_F_IOMMU_PLATFORM: Device can be used on IOMMU platform"),
    FEATURE_ENTRY(VIRTIO_F_RING_PACKED, \
            "VIRTIO_F_RING_PACKED: Device supports packed VQ layout"),
    FEATURE_ENTRY(VIRTIO_F_IN_ORDER, \
            "VIRTIO_F_IN_ORDER: Device uses buffers in same order as made "
            "available by driver"),
    FEATURE_ENTRY(VIRTIO_F_ORDER_PLATFORM, \
            "VIRTIO_F_ORDER_PLATFORM: Memory accesses ordered by platform"),
    FEATURE_ENTRY(VIRTIO_F_SR_IOV, \
            "VIRTIO_F_SR_IOV: Device supports single root I/O virtualization"),
    /* Virtio ring transport features */
    FEATURE_ENTRY(VIRTIO_RING_F_INDIRECT_DESC, \
            "VIRTIO_RING_F_INDIRECT_DESC: Indirect descriptors supported"),
    FEATURE_ENTRY(VIRTIO_RING_F_EVENT_IDX, \
            "VIRTIO_RING_F_EVENT_IDX: Used & avail. event fields enabled"),
    { -1, "" }
};

/* Vhost-user protocol features mapping */
static qmp_virtio_feature_map_t vhost_user_protocol_map[] = {
    FEATURE_ENTRY(VHOST_USER_PROTOCOL_F_MQ, \
            "VHOST_USER_PROTOCOL_F_MQ: Multiqueue protocol supported"),
    FEATURE_ENTRY(VHOST_USER_PROTOCOL_F_LOG_SHMFD, \
            "VHOST_USER_PROTOCOL_F_LOG_SHMFD: Shared log memory fd supported"),
    FEATURE_ENTRY(VHOST_USER_PROTOCOL_F_RARP, \
            "VHOST_USER_PROTOCOL_F_RARP: Vhost-user back-end RARP broadcasting "
            "supported"),
    FEATURE_ENTRY(VHOST_USER_PROTOCOL_F_REPLY_ACK, \
            "VHOST_USER_PROTOCOL_F_REPLY_ACK: Requested operation status ack. "
            "supported"),
    FEATURE_ENTRY(VHOST_USER_PROTOCOL_F_NET_MTU, \
            "VHOST_USER_PROTOCOL_F_NET_MTU: Expose host MTU to guest supported"),
    FEATURE_ENTRY(VHOST_USER_PROTOCOL_F_SLAVE_REQ, \
            "VHOST_USER_PROTOCOL_F_SLAVE_REQ: Socket fd for back-end initiated "
            "requests supported"),
    FEATURE_ENTRY(VHOST_USER_PROTOCOL_F_CROSS_ENDIAN, \
            "VHOST_USER_PROTOCOL_F_CROSS_ENDIAN: Endianness of VQs for legacy "
            "devices supported"),
    FEATURE_ENTRY(VHOST_USER_PROTOCOL_F_CRYPTO_SESSION, \
            "VHOST_USER_PROTOCOL_F_CRYPTO_SESSION: Session creation for crypto "
            "operations supported"),
    FEATURE_ENTRY(VHOST_USER_PROTOCOL_F_PAGEFAULT, \
            "VHOST_USER_PROTOCOL_F_PAGEFAULT: Request servicing on userfaultfd "
            "for accessed pages supported"),
    FEATURE_ENTRY(VHOST_USER_PROTOCOL_F_CONFIG, \
            "VHOST_USER_PROTOCOL_F_CONFIG: Vhost-user messaging for virtio "
            "device configuration space supported"),
    FEATURE_ENTRY(VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD, \
            "VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD: Slave fd communication "
            "channel supported"),
    FEATURE_ENTRY(VHOST_USER_PROTOCOL_F_HOST_NOTIFIER, \
            "VHOST_USER_PROTOCOL_F_HOST_NOTIFIER: Host notifiers for specified "
            "VQs supported"),
    FEATURE_ENTRY(VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD, \
            "VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD: Shared inflight I/O buffers "
            "supported"),
    FEATURE_ENTRY(VHOST_USER_PROTOCOL_F_RESET_DEVICE, \
            "VHOST_USER_PROTOCOL_F_RESET_DEVICE: Disabling all rings and "
            "resetting internal device state supported"),
    FEATURE_ENTRY(VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS, \
            "VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS: In-band messaging "
            "supported"),
    FEATURE_ENTRY(VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS, \
            "VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS: Configuration for "
            "memory slots supported"),
    { -1, "" }
};

/* virtio device configuration statuses */
static qmp_virtio_feature_map_t virtio_config_status_map[] = {
    FEATURE_ENTRY(VIRTIO_CONFIG_S_DRIVER_OK, \
            "VIRTIO_CONFIG_S_DRIVER_OK: Driver setup and ready"),
    FEATURE_ENTRY(VIRTIO_CONFIG_S_FEATURES_OK, \
            "VIRTIO_CONFIG_S_FEATURES_OK: Feature negotiation complete"),
    FEATURE_ENTRY(VIRTIO_CONFIG_S_DRIVER, \
            "VIRTIO_CONFIG_S_DRIVER: Guest OS compatible with device"),
    FEATURE_ENTRY(VIRTIO_CONFIG_S_NEEDS_RESET, \
            "VIRTIO_CONFIG_S_NEEDS_RESET: Irrecoverable error, device needs "
            "reset"),
    FEATURE_ENTRY(VIRTIO_CONFIG_S_FAILED, \
            "VIRTIO_CONFIG_S_FAILED: Error in guest, device failed"),
    FEATURE_ENTRY(VIRTIO_CONFIG_S_ACKNOWLEDGE, \
            "VIRTIO_CONFIG_S_ACKNOWLEDGE: Valid virtio device found"),
    { -1, "" }
};

/* virtio-blk features mapping */
qmp_virtio_feature_map_t virtio_blk_feature_map[] = {
    FEATURE_ENTRY(VIRTIO_BLK_F_SIZE_MAX, \
            "VIRTIO_BLK_F_SIZE_MAX: Max segment size is size_max"),
    FEATURE_ENTRY(VIRTIO_BLK_F_SEG_MAX, \
            "VIRTIO_BLK_F_SEG_MAX: Max segments in a request is seg_max"),
    FEATURE_ENTRY(VIRTIO_BLK_F_GEOMETRY, \
            "VIRTIO_BLK_F_GEOMETRY: Legacy geometry available"),
    FEATURE_ENTRY(VIRTIO_BLK_F_RO, \
            "VIRTIO_BLK_F_RO: Device is read-only"),
    FEATURE_ENTRY(VIRTIO_BLK_F_BLK_SIZE, \
            "VIRTIO_BLK_F_BLK_SIZE: Block size of disk available"),
    FEATURE_ENTRY(VIRTIO_BLK_F_TOPOLOGY, \
            "VIRTIO_BLK_F_TOPOLOGY: Topology information available"),
    FEATURE_ENTRY(VIRTIO_BLK_F_MQ, \
            "VIRTIO_BLK_F_MQ: Multiqueue supported"),
    FEATURE_ENTRY(VIRTIO_BLK_F_DISCARD, \
            "VIRTIO_BLK_F_DISCARD: Discard command supported"),
    FEATURE_ENTRY(VIRTIO_BLK_F_WRITE_ZEROES, \
            "VIRTIO_BLK_F_WRITE_ZEROES: Write zeroes command supported"),
#ifndef VIRTIO_BLK_NO_LEGACY
    FEATURE_ENTRY(VIRTIO_BLK_F_BARRIER, \
            "VIRTIO_BLK_F_BARRIER: Request barriers supported"),
    FEATURE_ENTRY(VIRTIO_BLK_F_SCSI, \
            "VIRTIO_BLK_F_SCSI: SCSI packet commands supported"),
    FEATURE_ENTRY(VIRTIO_BLK_F_FLUSH, \
            "VIRTIO_BLK_F_FLUSH: Flush command supported"),
    FEATURE_ENTRY(VIRTIO_BLK_F_CONFIG_WCE, \
            "VIRTIO_BLK_F_CONFIG_WCE: Cache writeback and writethrough modes "
            "supported"),
#endif /* !VIRTIO_BLK_NO_LEGACY */
    FEATURE_ENTRY(VHOST_F_LOG_ALL, \
            "VHOST_F_LOG_ALL: Logging write descriptors supported"),
    FEATURE_ENTRY(VHOST_USER_F_PROTOCOL_FEATURES, \
            "VHOST_USER_F_PROTOCOL_FEATURES: Vhost-user protocol features "
            "negotiation supported"),
    { -1, "" }
};

/* virtio-serial features mapping */
qmp_virtio_feature_map_t virtio_serial_feature_map[] = {
    FEATURE_ENTRY(VIRTIO_CONSOLE_F_SIZE, \
            "VIRTIO_CONSOLE_F_SIZE: Host providing console size"),
    FEATURE_ENTRY(VIRTIO_CONSOLE_F_MULTIPORT, \
            "VIRTIO_CONSOLE_F_MULTIPORT: Multiple ports for device supported"),
    FEATURE_ENTRY(VIRTIO_CONSOLE_F_EMERG_WRITE, \
            "VIRTIO_CONSOLE_F_EMERG_WRITE: Emergency write supported"),
    { -1, "" }
};

/* virtio-gpu features mapping */
qmp_virtio_feature_map_t virtio_gpu_feature_map[] = {
    FEATURE_ENTRY(VIRTIO_GPU_F_VIRGL, \
            "VIRTIO_GPU_F_VIRGL: Virgl 3D mode supported"),
    FEATURE_ENTRY(VIRTIO_GPU_F_EDID, \
            "VIRTIO_GPU_F_EDID: EDID metadata supported"),
    FEATURE_ENTRY(VIRTIO_GPU_F_RESOURCE_UUID, \
            "VIRTIO_GPU_F_RESOURCE_UUID: Resource UUID assigning supported"),
    FEATURE_ENTRY(VIRTIO_GPU_F_RESOURCE_BLOB, \
            "VIRTIO_GPU_F_RESOURCE_BLOB: Size-based blob resources supported"),
    FEATURE_ENTRY(VIRTIO_GPU_F_CONTEXT_INIT, \
            "VIRTIO_GPU_F_CONTEXT_INIT: Context types and synchronization "
            "timelines supported"),
    FEATURE_ENTRY(VHOST_F_LOG_ALL, \
            "VHOST_F_LOG_ALL: Logging write descriptors supported"),
    FEATURE_ENTRY(VHOST_USER_F_PROTOCOL_FEATURES, \
            "VHOST_USER_F_PROTOCOL_FEATURES: Vhost-user protocol features "
            "negotiation supported"),
    { -1, "" }
};

/* virtio-input features mapping */
qmp_virtio_feature_map_t virtio_input_feature_map[] = {
    FEATURE_ENTRY(VHOST_F_LOG_ALL, \
            "VHOST_F_LOG_ALL: Logging write descriptors supported"),
    FEATURE_ENTRY(VHOST_USER_F_PROTOCOL_FEATURES, \
            "VHOST_USER_F_PROTOCOL_FEATURES: Vhost-user protocol features "
            "negotiation supported"),
    { -1, "" }
};

/* virtio-net features mapping */
qmp_virtio_feature_map_t virtio_net_feature_map[] = {
    FEATURE_ENTRY(VIRTIO_NET_F_CSUM, \
            "VIRTIO_NET_F_CSUM: Device handling packets with partial checksum "
            "supported"),
    FEATURE_ENTRY(VIRTIO_NET_F_GUEST_CSUM, \
            "VIRTIO_NET_F_GUEST_CSUM: Driver handling packets with partial "
            "checksum supported"),
    FEATURE_ENTRY(VIRTIO_NET_F_CTRL_GUEST_OFFLOADS, \
            "VIRTIO_NET_F_CTRL_GUEST_OFFLOADS: Control channel offloading "
            "reconfig. supported"),
    FEATURE_ENTRY(VIRTIO_NET_F_MTU, \
            "VIRTIO_NET_F_MTU: Device max MTU reporting supported"),
    FEATURE_ENTRY(VIRTIO_NET_F_MAC, \
            "VIRTIO_NET_F_MAC: Device has given MAC address"),
    FEATURE_ENTRY(VIRTIO_NET_F_GUEST_TSO4, \
            "VIRTIO_NET_F_GUEST_TSO4: Driver can receive TSOv4"),
    FEATURE_ENTRY(VIRTIO_NET_F_GUEST_TSO6, \
            "VIRTIO_NET_F_GUEST_TSO6: Driver can receive TSOv6"),
    FEATURE_ENTRY(VIRTIO_NET_F_GUEST_ECN, \
            "VIRTIO_NET_F_GUEST_ECN: Driver can receive TSO with ECN"),
    FEATURE_ENTRY(VIRTIO_NET_F_GUEST_UFO, \
            "VIRTIO_NET_F_GUEST_UFO: Driver can receive UFO"),
    FEATURE_ENTRY(VIRTIO_NET_F_HOST_TSO4, \
            "VIRTIO_NET_F_HOST_TSO4: Device can receive TSOv4"),
    FEATURE_ENTRY(VIRTIO_NET_F_HOST_TSO6, \
            "VIRTIO_NET_F_HOST_TSO6: Device can receive TSOv6"),
    FEATURE_ENTRY(VIRTIO_NET_F_HOST_ECN, \
            "VIRTIO_NET_F_HOST_ECN: Device can receive TSO with ECN"),
    FEATURE_ENTRY(VIRTIO_NET_F_HOST_UFO, \
            "VIRTIO_NET_F_HOST_UFO: Device can receive UFO"),
    FEATURE_ENTRY(VIRTIO_NET_F_MRG_RXBUF, \
            "VIRTIO_NET_F_MRG_RXBUF: Driver can merge receive buffers"),
    FEATURE_ENTRY(VIRTIO_NET_F_STATUS, \
            "VIRTIO_NET_F_STATUS: Configuration status field available"),
    FEATURE_ENTRY(VIRTIO_NET_F_CTRL_VQ, \
            "VIRTIO_NET_F_CTRL_VQ: Control channel available"),
    FEATURE_ENTRY(VIRTIO_NET_F_CTRL_RX, \
            "VIRTIO_NET_F_CTRL_RX: Control channel RX mode supported"),
    FEATURE_ENTRY(VIRTIO_NET_F_CTRL_VLAN, \
            "VIRTIO_NET_F_CTRL_VLAN: Control channel VLAN filtering supported"),
    FEATURE_ENTRY(VIRTIO_NET_F_CTRL_RX_EXTRA, \
            "VIRTIO_NET_F_CTRL_RX_EXTRA: Extra RX mode control supported"),
    FEATURE_ENTRY(VIRTIO_NET_F_GUEST_ANNOUNCE, \
            "VIRTIO_NET_F_GUEST_ANNOUNCE: Driver sending gratuitous packets "
            "supported"),
    FEATURE_ENTRY(VIRTIO_NET_F_MQ, \
            "VIRTIO_NET_F_MQ: Multiqueue with automatic receive steering "
            "supported"),
    FEATURE_ENTRY(VIRTIO_NET_F_CTRL_MAC_ADDR, \
            "VIRTIO_NET_F_CTRL_MAC_ADDR: MAC address set through control "
            "channel"),
    FEATURE_ENTRY(VIRTIO_NET_F_HASH_REPORT, \
            "VIRTIO_NET_F_HASH_REPORT: Hash reporting supported"),
    FEATURE_ENTRY(VIRTIO_NET_F_RSS, \
            "VIRTIO_NET_F_RSS: RSS RX steering supported"),
    FEATURE_ENTRY(VIRTIO_NET_F_RSC_EXT, \
            "VIRTIO_NET_F_RSC_EXT: Extended coalescing info supported"),
    FEATURE_ENTRY(VIRTIO_NET_F_STANDBY, \
            "VIRTIO_NET_F_STANDBY: Device acting as standby for primary "
            "device with same MAC addr. supported"),
    FEATURE_ENTRY(VIRTIO_NET_F_SPEED_DUPLEX, \
            "VIRTIO_NET_F_SPEED_DUPLEX: Device set linkspeed and duplex"),
#ifndef VIRTIO_NET_NO_LEGACY
    FEATURE_ENTRY(VIRTIO_NET_F_GSO, \
            "VIRTIO_NET_F_GSO: Handling GSO-type packets supported"),
#endif /* !VIRTIO_NET_NO_LEGACY */
    FEATURE_ENTRY(VHOST_NET_F_VIRTIO_NET_HDR, \
            "VHOST_NET_F_VIRTIO_NET_HDR: Virtio-net headers for RX and TX "
            "packets supported"),
    FEATURE_ENTRY(VHOST_F_LOG_ALL, \
            "VHOST_F_LOG_ALL: Logging write descriptors supported"),
    FEATURE_ENTRY(VHOST_USER_F_PROTOCOL_FEATURES, \
            "VHOST_USER_F_PROTOCOL_FEATURES: Vhost-user protocol features "
            "negotiation supported"),
    { -1, "" }
};

/* virtio-scsi features mapping */
qmp_virtio_feature_map_t virtio_scsi_feature_map[] = {
    FEATURE_ENTRY(VIRTIO_SCSI_F_INOUT, \
            "VIRTIO_SCSI_F_INOUT: Requests including read and writable data "
            "buffers suppoted"),
    FEATURE_ENTRY(VIRTIO_SCSI_F_HOTPLUG, \
            "VIRTIO_SCSI_F_HOTPLUG: Reporting and handling hot-plug events "
            "supported"),
    FEATURE_ENTRY(VIRTIO_SCSI_F_CHANGE, \
            "VIRTIO_SCSI_F_CHANGE: Reporting and handling LUN changes "
            "supported"),
    FEATURE_ENTRY(VIRTIO_SCSI_F_T10_PI, \
            "VIRTIO_SCSI_F_T10_PI: T10 info included in request header"),
    FEATURE_ENTRY(VHOST_F_LOG_ALL, \
            "VHOST_F_LOG_ALL: Logging write descriptors supported"),
    FEATURE_ENTRY(VHOST_USER_F_PROTOCOL_FEATURES, \
            "VHOST_USER_F_PROTOCOL_FEATURES: Vhost-user protocol features "
            "negotiation supported"),
    { -1, "" }
};

/* virtio/vhost-user-fs features mapping */
qmp_virtio_feature_map_t virtio_fs_feature_map[] = {
    FEATURE_ENTRY(VHOST_F_LOG_ALL, \
            "VHOST_F_LOG_ALL: Logging write descriptors supported"),
    FEATURE_ENTRY(VHOST_USER_F_PROTOCOL_FEATURES, \
            "VHOST_USER_F_PROTOCOL_FEATURES: Vhost-user protocol features "
            "negotiation supported"),
    { -1, "" }
};

/* virtio/vhost-user-i2c features mapping */
qmp_virtio_feature_map_t virtio_i2c_feature_map[] = {
    FEATURE_ENTRY(VIRTIO_I2C_F_ZERO_LENGTH_REQUEST, \
            "VIRTIO_I2C_F_ZERO_LEGNTH_REQUEST: Zero length requests supported"),
    FEATURE_ENTRY(VHOST_F_LOG_ALL, \
            "VHOST_F_LOG_ALL: Logging write descriptors supported"),
    FEATURE_ENTRY(VHOST_USER_F_PROTOCOL_FEATURES, \
            "VHOST_USER_F_PROTOCOL_FEATURES: Vhost-user protocol features "
            "negotiation supported"),
    { -1, "" }
};

/* virtio/vhost-vsock features mapping */
qmp_virtio_feature_map_t virtio_vsock_feature_map[] = {
    FEATURE_ENTRY(VIRTIO_VSOCK_F_SEQPACKET, \
            "VIRTIO_VSOCK_F_SEQPACKET: SOCK_SEQPACKET supported"),
    FEATURE_ENTRY(VHOST_F_LOG_ALL, \
            "VHOST_F_LOG_ALL: Logging write descriptors supported"),
    FEATURE_ENTRY(VHOST_USER_F_PROTOCOL_FEATURES, \
            "VHOST_USER_F_PROTOCOL_FEATURES: Vhost-user protocol features "
            "negotiation supported"),
    { -1, "" }
};

/* virtio-balloon features mapping */
qmp_virtio_feature_map_t virtio_balloon_feature_map[] = {
    FEATURE_ENTRY(VIRTIO_BALLOON_F_MUST_TELL_HOST, \
            "VIRTIO_BALLOON_F_MUST_TELL_HOST: Tell host before reclaiming "
            "pages"),
    FEATURE_ENTRY(VIRTIO_BALLOON_F_STATS_VQ, \
            "VIRTIO_BALLOON_F_STATS_VQ: Guest memory stats VQ available"),
    FEATURE_ENTRY(VIRTIO_BALLOON_F_DEFLATE_ON_OOM, \
            "VIRTIO_BALLOON_F_DEFLATE_ON_OOM: Deflate balloon when guest OOM"),
    FEATURE_ENTRY(VIRTIO_BALLOON_F_FREE_PAGE_HINT, \
            "VIRTIO_BALLOON_F_FREE_PAGE_HINT: VQ reporting free pages enabled"),
    FEATURE_ENTRY(VIRTIO_BALLOON_F_PAGE_POISON, \
            "VIRTIO_BALLOON_F_PAGE_POISON: Guest page poisoning enabled"),
    FEATURE_ENTRY(VIRTIO_BALLOON_F_REPORTING, \
            "VIRTIO_BALLOON_F_REPORTING: Page reporting VQ enabled"),
    { -1, "" }
};

/* virtio-crypto features mapping */
qmp_virtio_feature_map_t virtio_crypto_feature_map[] = {
    FEATURE_ENTRY(VHOST_F_LOG_ALL, \
            "VHOST_F_LOG_ALL: Logging write descriptors supported"),
    { -1, "" }
};

/* virtio-iommu features mapping */
qmp_virtio_feature_map_t virtio_iommu_feature_map[] = {
    FEATURE_ENTRY(VIRTIO_IOMMU_F_INPUT_RANGE, \
            "VIRTIO_IOMMU_F_INPUT_RANGE: Range of available virtual addrs. "
            "available"),
    FEATURE_ENTRY(VIRTIO_IOMMU_F_DOMAIN_RANGE, \
            "VIRTIO_IOMMU_F_DOMAIN_RANGE: Number of supported domains "
            "available"),
    FEATURE_ENTRY(VIRTIO_IOMMU_F_MAP_UNMAP, \
            "VIRTIO_IOMMU_F_MAP_UNMAP: Map and unmap requests available"),
    FEATURE_ENTRY(VIRTIO_IOMMU_F_BYPASS, \
            "VIRTIO_IOMMU_F_BYPASS: Endpoints not attached to domains are in "
            "bypass mode"),
    FEATURE_ENTRY(VIRTIO_IOMMU_F_PROBE, \
            "VIRTIO_IOMMU_F_PROBE: Probe requests available"),
    FEATURE_ENTRY(VIRTIO_IOMMU_F_MMIO, \
            "VIRTIO_IOMMU_F_MMIO: VIRTIO_IOMMU_MAP_F_MMIO flag available"),
    FEATURE_ENTRY(VIRTIO_IOMMU_F_BYPASS_CONFIG, \
            "VIRTIO_IOMMU_F_BYPASS_CONFIG: Bypass field of IOMMU config "
            "available"),
    { -1, "" }
};

/* virtio-mem features mapping */
qmp_virtio_feature_map_t virtio_mem_feature_map[] = {
#ifndef CONFIG_ACPI
    FEATURE_ENTRY(VIRTIO_MEM_F_ACPI_PXM, \
            "VIRTIO_MEM_F_ACPI_PXM: node_id is an ACPI PXM and is valid"),
#endif /* !CONFIG_ACPI */
    FEATURE_ENTRY(VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE, \
            "VIRTIO_MEM_F_UNPLUGGED_INACCESSIBLE: Unplugged memory cannot be "
            "accessed"),
    { -1, "" }
};

/* virtio-rng features mapping */
qmp_virtio_feature_map_t virtio_rng_feature_map[] = {
    FEATURE_ENTRY(VHOST_F_LOG_ALL, \
            "VHOST_F_LOG_ALL: Logging write descriptors supported"),
    FEATURE_ENTRY(VHOST_USER_F_PROTOCOL_FEATURES, \
            "VHOST_USER_F_PROTOCOL_FEATURES: Vhost-user protocol features "
            "negotiation supported"),
    { -1, "" }
};

/*
 * The alignment to use between consumer and producer parts of vring.
 * x86 pagesize again. This is the default, used by transports like PCI
 * which don't provide a means for the guest to tell the host the alignment.
 */
#define VIRTIO_PCI_VRING_ALIGN         4096

typedef struct VRingDesc
{
    uint64_t addr;
    uint32_t len;
    uint16_t flags;
    uint16_t next;
} VRingDesc;

typedef struct VRingPackedDesc {
    uint64_t addr;
    uint32_t len;
    uint16_t id;
    uint16_t flags;
} VRingPackedDesc;

typedef struct VRingAvail
{
    uint16_t flags;
    uint16_t idx;
    uint16_t ring[];
} VRingAvail;

typedef struct VRingUsedElem
{
    uint32_t id;
    uint32_t len;
} VRingUsedElem;

typedef struct VRingUsed
{
    uint16_t flags;
    uint16_t idx;
    VRingUsedElem ring[];
} VRingUsed;

typedef struct VRingMemoryRegionCaches {
    struct rcu_head rcu;
    MemoryRegionCache desc;
    MemoryRegionCache avail;
    MemoryRegionCache used;
} VRingMemoryRegionCaches;

typedef struct VRing
{
    unsigned int num;
    unsigned int num_default;
    unsigned int align;
    hwaddr desc;
    hwaddr avail;
    hwaddr used;
    VRingMemoryRegionCaches *caches;
} VRing;

typedef struct VRingPackedDescEvent {
    uint16_t off_wrap;
    uint16_t flags;
} VRingPackedDescEvent ;

struct VirtQueue
{
    VRing vring;
    VirtQueueElement *used_elems;

    /* Next head to pop */
    uint16_t last_avail_idx;
    bool last_avail_wrap_counter;

    /* Last avail_idx read from VQ. */
    uint16_t shadow_avail_idx;
    bool shadow_avail_wrap_counter;

    uint16_t used_idx;
    bool used_wrap_counter;

    /* Last used index value we have signalled on */
    uint16_t signalled_used;

    /* Last used index value we have signalled on */
    bool signalled_used_valid;

    /* Notification enabled? */
    bool notification;

    uint16_t queue_index;

    unsigned int inuse;

    uint16_t vector;
    VirtIOHandleOutput handle_output;
    VirtIODevice *vdev;
    EventNotifier guest_notifier;
    EventNotifier host_notifier;
    bool host_notifier_enabled;
    QLIST_ENTRY(VirtQueue) node;
};

const char *virtio_device_names[] = {
    [VIRTIO_ID_NET] = "virtio-net",
    [VIRTIO_ID_BLOCK] = "virtio-blk",
    [VIRTIO_ID_CONSOLE] = "virtio-serial",
    [VIRTIO_ID_RNG] = "virtio-rng",
    [VIRTIO_ID_BALLOON] = "virtio-balloon",
    [VIRTIO_ID_IOMEM] = "virtio-iomem",
    [VIRTIO_ID_RPMSG] = "virtio-rpmsg",
    [VIRTIO_ID_SCSI] = "virtio-scsi",
    [VIRTIO_ID_9P] = "virtio-9p",
    [VIRTIO_ID_MAC80211_WLAN] = "virtio-mac-wlan",
    [VIRTIO_ID_RPROC_SERIAL] = "virtio-rproc-serial",
    [VIRTIO_ID_CAIF] = "virtio-caif",
    [VIRTIO_ID_MEMORY_BALLOON] = "virtio-mem-balloon",
    [VIRTIO_ID_GPU] = "virtio-gpu",
    [VIRTIO_ID_CLOCK] = "virtio-clk",
    [VIRTIO_ID_INPUT] = "virtio-input",
    [VIRTIO_ID_VSOCK] = "vhost-vsock",
    [VIRTIO_ID_CRYPTO] = "virtio-crypto",
    [VIRTIO_ID_SIGNAL_DIST] = "virtio-signal",
    [VIRTIO_ID_PSTORE] = "virtio-pstore",
    [VIRTIO_ID_IOMMU] = "virtio-iommu",
    [VIRTIO_ID_MEM] = "virtio-mem",
    [VIRTIO_ID_SOUND] = "virtio-sound",
    [VIRTIO_ID_FS] = "virtio-user-fs",
    [VIRTIO_ID_PMEM] = "virtio-pmem",
    [VIRTIO_ID_RPMB] = "virtio-rpmb",
    [VIRTIO_ID_MAC80211_HWSIM] = "virtio-mac-hwsim",
    [VIRTIO_ID_VIDEO_ENCODER] = "virtio-vid-encoder",
    [VIRTIO_ID_VIDEO_DECODER] = "virtio-vid-decoder",
    [VIRTIO_ID_SCMI] = "virtio-scmi",
    [VIRTIO_ID_NITRO_SEC_MOD] = "virtio-nitro-sec-mod",
    [VIRTIO_ID_I2C_ADAPTER] = "vhost-user-i2c",
    [VIRTIO_ID_WATCHDOG] = "virtio-watchdog",
    [VIRTIO_ID_CAN] = "virtio-can",
    [VIRTIO_ID_DMABUF] = "virtio-dmabuf",
    [VIRTIO_ID_PARAM_SERV] = "virtio-param-serv",
    [VIRTIO_ID_AUDIO_POLICY] = "virtio-audio-pol",
    [VIRTIO_ID_BT] = "virtio-bluetooth",
    [VIRTIO_ID_GPIO] = "virtio-gpio"
};

static const char *virtio_id_to_name(uint16_t device_id)
{
    assert(device_id < G_N_ELEMENTS(virtio_device_names));
    const char *name = virtio_device_names[device_id];
    assert(name != NULL);
    return name;
}

/* Called within call_rcu().  */
static void virtio_free_region_cache(VRingMemoryRegionCaches *caches)
{
    assert(caches != NULL);
    address_space_cache_destroy(&caches->desc);
    address_space_cache_destroy(&caches->avail);
    address_space_cache_destroy(&caches->used);
    g_free(caches);
}

static void virtio_virtqueue_reset_region_cache(struct VirtQueue *vq)
{
    VRingMemoryRegionCaches *caches;

    caches = qatomic_read(&vq->vring.caches);
    qatomic_rcu_set(&vq->vring.caches, NULL);
    if (caches) {
        call_rcu(caches, virtio_free_region_cache, rcu);
    }
}

static void virtio_init_region_cache(VirtIODevice *vdev, int n)
{
    VirtQueue *vq = &vdev->vq[n];
    VRingMemoryRegionCaches *old = vq->vring.caches;
    VRingMemoryRegionCaches *new = NULL;
    hwaddr addr, size;
    int64_t len;
    bool packed;


    addr = vq->vring.desc;
    if (!addr) {
        goto out_no_cache;
    }
    new = g_new0(VRingMemoryRegionCaches, 1);
    size = virtio_queue_get_desc_size(vdev, n);
    packed = virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED) ?
                                   true : false;
    len = address_space_cache_init(&new->desc, vdev->dma_as,
                                   addr, size, packed);
    if (len < size) {
        virtio_error(vdev, "Cannot map desc");
        goto err_desc;
    }

    size = virtio_queue_get_used_size(vdev, n);
    len = address_space_cache_init(&new->used, vdev->dma_as,
                                   vq->vring.used, size, true);
    if (len < size) {
        virtio_error(vdev, "Cannot map used");
        goto err_used;
    }

    size = virtio_queue_get_avail_size(vdev, n);
    len = address_space_cache_init(&new->avail, vdev->dma_as,
                                   vq->vring.avail, size, false);
    if (len < size) {
        virtio_error(vdev, "Cannot map avail");
        goto err_avail;
    }

    qatomic_rcu_set(&vq->vring.caches, new);
    if (old) {
        call_rcu(old, virtio_free_region_cache, rcu);
    }
    return;

err_avail:
    address_space_cache_destroy(&new->avail);
err_used:
    address_space_cache_destroy(&new->used);
err_desc:
    address_space_cache_destroy(&new->desc);
out_no_cache:
    g_free(new);
    virtio_virtqueue_reset_region_cache(vq);
}

/* virt queue functions */
void virtio_queue_update_rings(VirtIODevice *vdev, int n)
{
    VRing *vring = &vdev->vq[n].vring;

    if (!vring->num || !vring->desc || !vring->align) {
        /* not yet setup -> nothing to do */
        return;
    }
    vring->avail = vring->desc + vring->num * sizeof(VRingDesc);
    vring->used = vring_align(vring->avail +
                              offsetof(VRingAvail, ring[vring->num]),
                              vring->align);
    virtio_init_region_cache(vdev, n);
}

/* Called within rcu_read_lock().  */
static void vring_split_desc_read(VirtIODevice *vdev, VRingDesc *desc,
                                  MemoryRegionCache *cache, int i)
{
    address_space_read_cached(cache, i * sizeof(VRingDesc),
                              desc, sizeof(VRingDesc));
    virtio_tswap64s(vdev, &desc->addr);
    virtio_tswap32s(vdev, &desc->len);
    virtio_tswap16s(vdev, &desc->flags);
    virtio_tswap16s(vdev, &desc->next);
}

static void vring_packed_event_read(VirtIODevice *vdev,
                                    MemoryRegionCache *cache,
                                    VRingPackedDescEvent *e)
{
    hwaddr off_off = offsetof(VRingPackedDescEvent, off_wrap);
    hwaddr off_flags = offsetof(VRingPackedDescEvent, flags);

    e->flags = virtio_lduw_phys_cached(vdev, cache, off_flags);
    /* Make sure flags is seen before off_wrap */
    smp_rmb();
    e->off_wrap = virtio_lduw_phys_cached(vdev, cache, off_off);
    virtio_tswap16s(vdev, &e->flags);
}

static void vring_packed_off_wrap_write(VirtIODevice *vdev,
                                        MemoryRegionCache *cache,
                                        uint16_t off_wrap)
{
    hwaddr off = offsetof(VRingPackedDescEvent, off_wrap);

    virtio_stw_phys_cached(vdev, cache, off, off_wrap);
    address_space_cache_invalidate(cache, off, sizeof(off_wrap));
}

static void vring_packed_flags_write(VirtIODevice *vdev,
                                     MemoryRegionCache *cache, uint16_t flags)
{
    hwaddr off = offsetof(VRingPackedDescEvent, flags);

    virtio_stw_phys_cached(vdev, cache, off, flags);
    address_space_cache_invalidate(cache, off, sizeof(flags));
}

/* Called within rcu_read_lock().  */
static VRingMemoryRegionCaches *vring_get_region_caches(struct VirtQueue *vq)
{
    return qatomic_rcu_read(&vq->vring.caches);
}

/* Called within rcu_read_lock().  */
static inline uint16_t vring_avail_flags(VirtQueue *vq)
{
    VRingMemoryRegionCaches *caches = vring_get_region_caches(vq);
    hwaddr pa = offsetof(VRingAvail, flags);

    if (!caches) {
        return 0;
    }

    return virtio_lduw_phys_cached(vq->vdev, &caches->avail, pa);
}

/* Called within rcu_read_lock().  */
static inline uint16_t vring_avail_idx(VirtQueue *vq)
{
    VRingMemoryRegionCaches *caches = vring_get_region_caches(vq);
    hwaddr pa = offsetof(VRingAvail, idx);

    if (!caches) {
        return 0;
    }

    vq->shadow_avail_idx = virtio_lduw_phys_cached(vq->vdev, &caches->avail, pa);
    return vq->shadow_avail_idx;
}

/* Called within rcu_read_lock().  */
static inline uint16_t vring_avail_ring(VirtQueue *vq, int i)
{
    VRingMemoryRegionCaches *caches = vring_get_region_caches(vq);
    hwaddr pa = offsetof(VRingAvail, ring[i]);

    if (!caches) {
        return 0;
    }

    return virtio_lduw_phys_cached(vq->vdev, &caches->avail, pa);
}

/* Called within rcu_read_lock().  */
static inline uint16_t vring_get_used_event(VirtQueue *vq)
{
    return vring_avail_ring(vq, vq->vring.num);
}

/* Called within rcu_read_lock().  */
static inline void vring_used_write(VirtQueue *vq, VRingUsedElem *uelem,
                                    int i)
{
    VRingMemoryRegionCaches *caches = vring_get_region_caches(vq);
    hwaddr pa = offsetof(VRingUsed, ring[i]);

    if (!caches) {
        return;
    }

    virtio_tswap32s(vq->vdev, &uelem->id);
    virtio_tswap32s(vq->vdev, &uelem->len);
    address_space_write_cached(&caches->used, pa, uelem, sizeof(VRingUsedElem));
    address_space_cache_invalidate(&caches->used, pa, sizeof(VRingUsedElem));
}

/* Called within rcu_read_lock(). */
static inline uint16_t vring_used_flags(VirtQueue *vq)
{
    VRingMemoryRegionCaches *caches = vring_get_region_caches(vq);
    hwaddr pa = offsetof(VRingUsed, flags);

    if (!caches) {
        return 0;
    }

    return virtio_lduw_phys_cached(vq->vdev, &caches->used, pa);
}

/* Called within rcu_read_lock().  */
static uint16_t vring_used_idx(VirtQueue *vq)
{
    VRingMemoryRegionCaches *caches = vring_get_region_caches(vq);
    hwaddr pa = offsetof(VRingUsed, idx);

    if (!caches) {
        return 0;
    }

    return virtio_lduw_phys_cached(vq->vdev, &caches->used, pa);
}

/* Called within rcu_read_lock().  */
static inline void vring_used_idx_set(VirtQueue *vq, uint16_t val)
{
    VRingMemoryRegionCaches *caches = vring_get_region_caches(vq);
    hwaddr pa = offsetof(VRingUsed, idx);

    if (caches) {
        virtio_stw_phys_cached(vq->vdev, &caches->used, pa, val);
        address_space_cache_invalidate(&caches->used, pa, sizeof(val));
    }

    vq->used_idx = val;
}

/* Called within rcu_read_lock().  */
static inline void vring_used_flags_set_bit(VirtQueue *vq, int mask)
{
    VRingMemoryRegionCaches *caches = vring_get_region_caches(vq);
    VirtIODevice *vdev = vq->vdev;
    hwaddr pa = offsetof(VRingUsed, flags);
    uint16_t flags;

    if (!caches) {
        return;
    }

    flags = virtio_lduw_phys_cached(vq->vdev, &caches->used, pa);
    virtio_stw_phys_cached(vdev, &caches->used, pa, flags | mask);
    address_space_cache_invalidate(&caches->used, pa, sizeof(flags));
}

/* Called within rcu_read_lock().  */
static inline void vring_used_flags_unset_bit(VirtQueue *vq, int mask)
{
    VRingMemoryRegionCaches *caches = vring_get_region_caches(vq);
    VirtIODevice *vdev = vq->vdev;
    hwaddr pa = offsetof(VRingUsed, flags);
    uint16_t flags;

    if (!caches) {
        return;
    }

    flags = virtio_lduw_phys_cached(vq->vdev, &caches->used, pa);
    virtio_stw_phys_cached(vdev, &caches->used, pa, flags & ~mask);
    address_space_cache_invalidate(&caches->used, pa, sizeof(flags));
}

/* Called within rcu_read_lock().  */
static inline void vring_set_avail_event(VirtQueue *vq, uint16_t val)
{
    VRingMemoryRegionCaches *caches;
    hwaddr pa;
    if (!vq->notification) {
        return;
    }

    caches = vring_get_region_caches(vq);
    if (!caches) {
        return;
    }

    pa = offsetof(VRingUsed, ring[vq->vring.num]);
    virtio_stw_phys_cached(vq->vdev, &caches->used, pa, val);
    address_space_cache_invalidate(&caches->used, pa, sizeof(val));
}

static void virtio_queue_split_set_notification(VirtQueue *vq, int enable)
{
    RCU_READ_LOCK_GUARD();

    if (virtio_vdev_has_feature(vq->vdev, VIRTIO_RING_F_EVENT_IDX)) {
        vring_set_avail_event(vq, vring_avail_idx(vq));
    } else if (enable) {
        vring_used_flags_unset_bit(vq, VRING_USED_F_NO_NOTIFY);
    } else {
        vring_used_flags_set_bit(vq, VRING_USED_F_NO_NOTIFY);
    }
    if (enable) {
        /* Expose avail event/used flags before caller checks the avail idx. */
        smp_mb();
    }
}

static void virtio_queue_packed_set_notification(VirtQueue *vq, int enable)
{
    uint16_t off_wrap;
    VRingPackedDescEvent e;
    VRingMemoryRegionCaches *caches;

    RCU_READ_LOCK_GUARD();
    caches = vring_get_region_caches(vq);
    if (!caches) {
        return;
    }

    vring_packed_event_read(vq->vdev, &caches->used, &e);

    if (!enable) {
        e.flags = VRING_PACKED_EVENT_FLAG_DISABLE;
    } else if (virtio_vdev_has_feature(vq->vdev, VIRTIO_RING_F_EVENT_IDX)) {
        off_wrap = vq->shadow_avail_idx | vq->shadow_avail_wrap_counter << 15;
        vring_packed_off_wrap_write(vq->vdev, &caches->used, off_wrap);
        /* Make sure off_wrap is wrote before flags */
        smp_wmb();
        e.flags = VRING_PACKED_EVENT_FLAG_DESC;
    } else {
        e.flags = VRING_PACKED_EVENT_FLAG_ENABLE;
    }

    vring_packed_flags_write(vq->vdev, &caches->used, e.flags);
    if (enable) {
        /* Expose avail event/used flags before caller checks the avail idx. */
        smp_mb();
    }
}

bool virtio_queue_get_notification(VirtQueue *vq)
{
    return vq->notification;
}

void virtio_queue_set_notification(VirtQueue *vq, int enable)
{
    vq->notification = enable;

    if (!vq->vring.desc) {
        return;
    }

    if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) {
        virtio_queue_packed_set_notification(vq, enable);
    } else {
        virtio_queue_split_set_notification(vq, enable);
    }
}

int virtio_queue_ready(VirtQueue *vq)
{
    return vq->vring.avail != 0;
}

static void vring_packed_desc_read_flags(VirtIODevice *vdev,
                                         uint16_t *flags,
                                         MemoryRegionCache *cache,
                                         int i)
{
    hwaddr off = i * sizeof(VRingPackedDesc) + offsetof(VRingPackedDesc, flags);

    *flags = virtio_lduw_phys_cached(vdev, cache, off);
}

static void vring_packed_desc_read(VirtIODevice *vdev,
                                   VRingPackedDesc *desc,
                                   MemoryRegionCache *cache,
                                   int i, bool strict_order)
{
    hwaddr off = i * sizeof(VRingPackedDesc);

    vring_packed_desc_read_flags(vdev, &desc->flags, cache, i);

    if (strict_order) {
        /* Make sure flags is read before the rest fields. */
        smp_rmb();
    }

    address_space_read_cached(cache, off + offsetof(VRingPackedDesc, addr),
                              &desc->addr, sizeof(desc->addr));
    address_space_read_cached(cache, off + offsetof(VRingPackedDesc, id),
                              &desc->id, sizeof(desc->id));
    address_space_read_cached(cache, off + offsetof(VRingPackedDesc, len),
                              &desc->len, sizeof(desc->len));
    virtio_tswap64s(vdev, &desc->addr);
    virtio_tswap16s(vdev, &desc->id);
    virtio_tswap32s(vdev, &desc->len);
}

static void vring_packed_desc_write_data(VirtIODevice *vdev,
                                         VRingPackedDesc *desc,
                                         MemoryRegionCache *cache,
                                         int i)
{
    hwaddr off_id = i * sizeof(VRingPackedDesc) +
                    offsetof(VRingPackedDesc, id);
    hwaddr off_len = i * sizeof(VRingPackedDesc) +
                    offsetof(VRingPackedDesc, len);

    virtio_tswap32s(vdev, &desc->len);
    virtio_tswap16s(vdev, &desc->id);
    address_space_write_cached(cache, off_id, &desc->id, sizeof(desc->id));
    address_space_cache_invalidate(cache, off_id, sizeof(desc->id));
    address_space_write_cached(cache, off_len, &desc->len, sizeof(desc->len));
    address_space_cache_invalidate(cache, off_len, sizeof(desc->len));
}

static void vring_packed_desc_write_flags(VirtIODevice *vdev,
                                          VRingPackedDesc *desc,
                                          MemoryRegionCache *cache,
                                          int i)
{
    hwaddr off = i * sizeof(VRingPackedDesc) + offsetof(VRingPackedDesc, flags);

    virtio_stw_phys_cached(vdev, cache, off, desc->flags);
    address_space_cache_invalidate(cache, off, sizeof(desc->flags));
}

static void vring_packed_desc_write(VirtIODevice *vdev,
                                    VRingPackedDesc *desc,
                                    MemoryRegionCache *cache,
                                    int i, bool strict_order)
{
    vring_packed_desc_write_data(vdev, desc, cache, i);
    if (strict_order) {
        /* Make sure data is wrote before flags. */
        smp_wmb();
    }
    vring_packed_desc_write_flags(vdev, desc, cache, i);
}

static inline bool is_desc_avail(uint16_t flags, bool wrap_counter)
{
    bool avail, used;

    avail = !!(flags & (1 << VRING_PACKED_DESC_F_AVAIL));
    used = !!(flags & (1 << VRING_PACKED_DESC_F_USED));
    return (avail != used) && (avail == wrap_counter);
}

/* Fetch avail_idx from VQ memory only when we really need to know if
 * guest has added some buffers.
 * Called within rcu_read_lock().  */
static int virtio_queue_empty_rcu(VirtQueue *vq)
{
    if (virtio_device_disabled(vq->vdev)) {
        return 1;
    }

    if (unlikely(!vq->vring.avail)) {
        return 1;
    }

    if (vq->shadow_avail_idx != vq->last_avail_idx) {
        return 0;
    }

    return vring_avail_idx(vq) == vq->last_avail_idx;
}

static int virtio_queue_split_empty(VirtQueue *vq)
{
    bool empty;

    if (virtio_device_disabled(vq->vdev)) {
        return 1;
    }

    if (unlikely(!vq->vring.avail)) {
        return 1;
    }

    if (vq->shadow_avail_idx != vq->last_avail_idx) {
        return 0;
    }

    RCU_READ_LOCK_GUARD();
    empty = vring_avail_idx(vq) == vq->last_avail_idx;
    return empty;
}

/* Called within rcu_read_lock().  */
static int virtio_queue_packed_empty_rcu(VirtQueue *vq)
{
    struct VRingPackedDesc desc;
    VRingMemoryRegionCaches *cache;

    if (unlikely(!vq->vring.desc)) {
        return 1;
    }

    cache = vring_get_region_caches(vq);
    if (!cache) {
        return 1;
    }

    vring_packed_desc_read_flags(vq->vdev, &desc.flags, &cache->desc,
                                 vq->last_avail_idx);

    return !is_desc_avail(desc.flags, vq->last_avail_wrap_counter);
}

static int virtio_queue_packed_empty(VirtQueue *vq)
{
    RCU_READ_LOCK_GUARD();
    return virtio_queue_packed_empty_rcu(vq);
}

int virtio_queue_empty(VirtQueue *vq)
{
    if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) {
        return virtio_queue_packed_empty(vq);
    } else {
        return virtio_queue_split_empty(vq);
    }
}

static void virtqueue_unmap_sg(VirtQueue *vq, const VirtQueueElement *elem,
                               unsigned int len)
{
    AddressSpace *dma_as = vq->vdev->dma_as;
    unsigned int offset;
    int i;

    offset = 0;
    for (i = 0; i < elem->in_num; i++) {
        size_t size = MIN(len - offset, elem->in_sg[i].iov_len);

        dma_memory_unmap(dma_as, elem->in_sg[i].iov_base,
                         elem->in_sg[i].iov_len,
                         DMA_DIRECTION_FROM_DEVICE, size);

        offset += size;
    }

    for (i = 0; i < elem->out_num; i++)
        dma_memory_unmap(dma_as, elem->out_sg[i].iov_base,
                         elem->out_sg[i].iov_len,
                         DMA_DIRECTION_TO_DEVICE,
                         elem->out_sg[i].iov_len);
}

/* virtqueue_detach_element:
 * @vq: The #VirtQueue
 * @elem: The #VirtQueueElement
 * @len: number of bytes written
 *
 * Detach the element from the virtqueue.  This function is suitable for device
 * reset or other situations where a #VirtQueueElement is simply freed and will
 * not be pushed or discarded.
 */
void virtqueue_detach_element(VirtQueue *vq, const VirtQueueElement *elem,
                              unsigned int len)
{
    vq->inuse -= elem->ndescs;
    virtqueue_unmap_sg(vq, elem, len);
}

static void virtqueue_split_rewind(VirtQueue *vq, unsigned int num)
{
    vq->last_avail_idx -= num;
}

static void virtqueue_packed_rewind(VirtQueue *vq, unsigned int num)
{
    if (vq->last_avail_idx < num) {
        vq->last_avail_idx = vq->vring.num + vq->last_avail_idx - num;
        vq->last_avail_wrap_counter ^= 1;
    } else {
        vq->last_avail_idx -= num;
    }
}

/* virtqueue_unpop:
 * @vq: The #VirtQueue
 * @elem: The #VirtQueueElement
 * @len: number of bytes written
 *
 * Pretend the most recent element wasn't popped from the virtqueue.  The next
 * call to virtqueue_pop() will refetch the element.
 */
void virtqueue_unpop(VirtQueue *vq, const VirtQueueElement *elem,
                     unsigned int len)
{

    if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) {
        virtqueue_packed_rewind(vq, 1);
    } else {
        virtqueue_split_rewind(vq, 1);
    }

    virtqueue_detach_element(vq, elem, len);
}

/* virtqueue_rewind:
 * @vq: The #VirtQueue
 * @num: Number of elements to push back
 *
 * Pretend that elements weren't popped from the virtqueue.  The next
 * virtqueue_pop() will refetch the oldest element.
 *
 * Use virtqueue_unpop() instead if you have a VirtQueueElement.
 *
 * Returns: true on success, false if @num is greater than the number of in use
 * elements.
 */
bool virtqueue_rewind(VirtQueue *vq, unsigned int num)
{
    if (num > vq->inuse) {
        return false;
    }

    vq->inuse -= num;
    if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) {
        virtqueue_packed_rewind(vq, num);
    } else {
        virtqueue_split_rewind(vq, num);
    }
    return true;
}

static void virtqueue_split_fill(VirtQueue *vq, const VirtQueueElement *elem,
                    unsigned int len, unsigned int idx)
{
    VRingUsedElem uelem;

    if (unlikely(!vq->vring.used)) {
        return;
    }

    idx = (idx + vq->used_idx) % vq->vring.num;

    uelem.id = elem->index;
    uelem.len = len;
    vring_used_write(vq, &uelem, idx);
}

static void virtqueue_packed_fill(VirtQueue *vq, const VirtQueueElement *elem,
                                  unsigned int len, unsigned int idx)
{
    vq->used_elems[idx].index = elem->index;
    vq->used_elems[idx].len = len;
    vq->used_elems[idx].ndescs = elem->ndescs;
}

static void virtqueue_packed_fill_desc(VirtQueue *vq,
                                       const VirtQueueElement *elem,
                                       unsigned int idx,
                                       bool strict_order)
{
    uint16_t head;
    VRingMemoryRegionCaches *caches;
    VRingPackedDesc desc = {
        .id = elem->index,
        .len = elem->len,
    };
    bool wrap_counter = vq->used_wrap_counter;

    if (unlikely(!vq->vring.desc)) {
        return;
    }

    head = vq->used_idx + idx;
    if (head >= vq->vring.num) {
        head -= vq->vring.num;
        wrap_counter ^= 1;
    }
    if (wrap_counter) {
        desc.flags |= (1 << VRING_PACKED_DESC_F_AVAIL);
        desc.flags |= (1 << VRING_PACKED_DESC_F_USED);
    } else {
        desc.flags &= ~(1 << VRING_PACKED_DESC_F_AVAIL);
        desc.flags &= ~(1 << VRING_PACKED_DESC_F_USED);
    }

    caches = vring_get_region_caches(vq);
    if (!caches) {
        return;
    }

    vring_packed_desc_write(vq->vdev, &desc, &caches->desc, head, strict_order);
}

/* Called within rcu_read_lock().  */
void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
                    unsigned int len, unsigned int idx)
{
    trace_virtqueue_fill(vq, elem, len, idx);

    virtqueue_unmap_sg(vq, elem, len);

    if (virtio_device_disabled(vq->vdev)) {
        return;
    }

    if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) {
        virtqueue_packed_fill(vq, elem, len, idx);
    } else {
        virtqueue_split_fill(vq, elem, len, idx);
    }
}

/* Called within rcu_read_lock().  */
static void virtqueue_split_flush(VirtQueue *vq, unsigned int count)
{
    uint16_t old, new;

    if (unlikely(!vq->vring.used)) {
        return;
    }

    /* Make sure buffer is written before we update index. */
    smp_wmb();
    trace_virtqueue_flush(vq, count);
    old = vq->used_idx;
    new = old + count;
    vring_used_idx_set(vq, new);
    vq->inuse -= count;
    if (unlikely((int16_t)(new - vq->signalled_used) < (uint16_t)(new - old)))
        vq->signalled_used_valid = false;
}

static void virtqueue_packed_flush(VirtQueue *vq, unsigned int count)
{
    unsigned int i, ndescs = 0;

    if (unlikely(!vq->vring.desc)) {
        return;
    }

    for (i = 1; i < count; i++) {
        virtqueue_packed_fill_desc(vq, &vq->used_elems[i], i, false);
        ndescs += vq->used_elems[i].ndescs;
    }
    virtqueue_packed_fill_desc(vq, &vq->used_elems[0], 0, true);
    ndescs += vq->used_elems[0].ndescs;

    vq->inuse -= ndescs;
    vq->used_idx += ndescs;
    if (vq->used_idx >= vq->vring.num) {
        vq->used_idx -= vq->vring.num;
        vq->used_wrap_counter ^= 1;
        vq->signalled_used_valid = false;
    }
}

void virtqueue_flush(VirtQueue *vq, unsigned int count)
{
    if (virtio_device_disabled(vq->vdev)) {
        vq->inuse -= count;
        return;
    }

    if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) {
        virtqueue_packed_flush(vq, count);
    } else {
        virtqueue_split_flush(vq, count);
    }
}

void virtqueue_push(VirtQueue *vq, const VirtQueueElement *elem,
                    unsigned int len)
{
    RCU_READ_LOCK_GUARD();
    virtqueue_fill(vq, elem, len, 0);
    virtqueue_flush(vq, 1);
}

/* Called within rcu_read_lock().  */
static int virtqueue_num_heads(VirtQueue *vq, unsigned int idx)
{
    uint16_t num_heads = vring_avail_idx(vq) - idx;

    /* Check it isn't doing very strange things with descriptor numbers. */
    if (num_heads > vq->vring.num) {
        virtio_error(vq->vdev, "Guest moved used index from %u to %u",
                     idx, vq->shadow_avail_idx);
        return -EINVAL;
    }
    /* On success, callers read a descriptor at vq->last_avail_idx.
     * Make sure descriptor read does not bypass avail index read. */
    if (num_heads) {
        smp_rmb();
    }

    return num_heads;
}

/* Called within rcu_read_lock().  */
static bool virtqueue_get_head(VirtQueue *vq, unsigned int idx,
                               unsigned int *head)
{
    /* Grab the next descriptor number they're advertising, and increment
     * the index we've seen. */
    *head = vring_avail_ring(vq, idx % vq->vring.num);

    /* If their number is silly, that's a fatal mistake. */
    if (*head >= vq->vring.num) {
        virtio_error(vq->vdev, "Guest says index %u is available", *head);
        return false;
    }

    return true;
}

enum {
    VIRTQUEUE_READ_DESC_ERROR = -1,
    VIRTQUEUE_READ_DESC_DONE = 0,   /* end of chain */
    VIRTQUEUE_READ_DESC_MORE = 1,   /* more buffers in chain */
};

static int virtqueue_split_read_next_desc(VirtIODevice *vdev, VRingDesc *desc,
                                          MemoryRegionCache *desc_cache,
                                          unsigned int max, unsigned int *next)
{
    /* If this descriptor says it doesn't chain, we're done. */
    if (!(desc->flags & VRING_DESC_F_NEXT)) {
        return VIRTQUEUE_READ_DESC_DONE;
    }

    /* Check they're not leading us off end of descriptors. */
    *next = desc->next;
    /* Make sure compiler knows to grab that: we don't want it changing! */
    smp_wmb();

    if (*next >= max) {
        virtio_error(vdev, "Desc next is %u", *next);
        return VIRTQUEUE_READ_DESC_ERROR;
    }

    vring_split_desc_read(vdev, desc, desc_cache, *next);
    return VIRTQUEUE_READ_DESC_MORE;
}

/* Called within rcu_read_lock().  */
static void virtqueue_split_get_avail_bytes(VirtQueue *vq,
                            unsigned int *in_bytes, unsigned int *out_bytes,
                            unsigned max_in_bytes, unsigned max_out_bytes,
                            VRingMemoryRegionCaches *caches)
{
    VirtIODevice *vdev = vq->vdev;
    unsigned int max, idx;
    unsigned int total_bufs, in_total, out_total;
    MemoryRegionCache indirect_desc_cache = MEMORY_REGION_CACHE_INVALID;
    int64_t len = 0;
    int rc;

    idx = vq->last_avail_idx;
    total_bufs = in_total = out_total = 0;

    max = vq->vring.num;

    while ((rc = virtqueue_num_heads(vq, idx)) > 0) {
        MemoryRegionCache *desc_cache = &caches->desc;
        unsigned int num_bufs;
        VRingDesc desc;
        unsigned int i;

        num_bufs = total_bufs;

        if (!virtqueue_get_head(vq, idx++, &i)) {
            goto err;
        }

        vring_split_desc_read(vdev, &desc, desc_cache, i);

        if (desc.flags & VRING_DESC_F_INDIRECT) {
            if (!desc.len || (desc.len % sizeof(VRingDesc))) {
                virtio_error(vdev, "Invalid size for indirect buffer table");
                goto err;
            }

            /* If we've got too many, that implies a descriptor loop. */
            if (num_bufs >= max) {
                virtio_error(vdev, "Looped descriptor");
                goto err;
            }

            /* loop over the indirect descriptor table */
            len = address_space_cache_init(&indirect_desc_cache,
                                           vdev->dma_as,
                                           desc.addr, desc.len, false);
            desc_cache = &indirect_desc_cache;
            if (len < desc.len) {
                virtio_error(vdev, "Cannot map indirect buffer");
                goto err;
            }

            max = desc.len / sizeof(VRingDesc);
            num_bufs = i = 0;
            vring_split_desc_read(vdev, &desc, desc_cache, i);
        }

        do {
            /* If we've got too many, that implies a descriptor loop. */
            if (++num_bufs > max) {
                virtio_error(vdev, "Looped descriptor");
                goto err;
            }

            if (desc.flags & VRING_DESC_F_WRITE) {
                in_total += desc.len;
            } else {
                out_total += desc.len;
            }
            if (in_total >= max_in_bytes && out_total >= max_out_bytes) {
                goto done;
            }

            rc = virtqueue_split_read_next_desc(vdev, &desc, desc_cache, max, &i);
        } while (rc == VIRTQUEUE_READ_DESC_MORE);

        if (rc == VIRTQUEUE_READ_DESC_ERROR) {
            goto err;
        }

        if (desc_cache == &indirect_desc_cache) {
            address_space_cache_destroy(&indirect_desc_cache);
            total_bufs++;
        } else {
            total_bufs = num_bufs;
        }
    }

    if (rc < 0) {
        goto err;
    }

done:
    address_space_cache_destroy(&indirect_desc_cache);
    if (in_bytes) {
        *in_bytes = in_total;
    }
    if (out_bytes) {
        *out_bytes = out_total;
    }
    return;

err:
    in_total = out_total = 0;
    goto done;
}

static int virtqueue_packed_read_next_desc(VirtQueue *vq,
                                           VRingPackedDesc *desc,
                                           MemoryRegionCache
                                           *desc_cache,
                                           unsigned int max,
                                           unsigned int *next,
                                           bool indirect)
{
    /* If this descriptor says it doesn't chain, we're done. */
    if (!indirect && !(desc->flags & VRING_DESC_F_NEXT)) {
        return VIRTQUEUE_READ_DESC_DONE;
    }

    ++*next;
    if (*next == max) {
        if (indirect) {
            return VIRTQUEUE_READ_DESC_DONE;
        } else {
            (*next) -= vq->vring.num;
        }
    }

    vring_packed_desc_read(vq->vdev, desc, desc_cache, *next, false);
    return VIRTQUEUE_READ_DESC_MORE;
}

/* Called within rcu_read_lock().  */
static void virtqueue_packed_get_avail_bytes(VirtQueue *vq,
                                             unsigned int *in_bytes,
                                             unsigned int *out_bytes,
                                             unsigned max_in_bytes,
                                             unsigned max_out_bytes,
                                             VRingMemoryRegionCaches *caches)
{
    VirtIODevice *vdev = vq->vdev;
    unsigned int max, idx;
    unsigned int total_bufs, in_total, out_total;
    MemoryRegionCache *desc_cache;
    MemoryRegionCache indirect_desc_cache = MEMORY_REGION_CACHE_INVALID;
    int64_t len = 0;
    VRingPackedDesc desc;
    bool wrap_counter;

    idx = vq->last_avail_idx;
    wrap_counter = vq->last_avail_wrap_counter;
    total_bufs = in_total = out_total = 0;

    max = vq->vring.num;

    for (;;) {
        unsigned int num_bufs = total_bufs;
        unsigned int i = idx;
        int rc;

        desc_cache = &caches->desc;
        vring_packed_desc_read(vdev, &desc, desc_cache, idx, true);
        if (!is_desc_avail(desc.flags, wrap_counter)) {
            break;
        }

        if (desc.flags & VRING_DESC_F_INDIRECT) {
            if (desc.len % sizeof(VRingPackedDesc)) {
                virtio_error(vdev, "Invalid size for indirect buffer table");
                goto err;
            }

            /* If we've got too many, that implies a descriptor loop. */
            if (num_bufs >= max) {
                virtio_error(vdev, "Looped descriptor");
                goto err;
            }

            /* loop over the indirect descriptor table */
            len = address_space_cache_init(&indirect_desc_cache,
                                           vdev->dma_as,
                                           desc.addr, desc.len, false);
            desc_cache = &indirect_desc_cache;
            if (len < desc.len) {
                virtio_error(vdev, "Cannot map indirect buffer");
                goto err;
            }

            max = desc.len / sizeof(VRingPackedDesc);
            num_bufs = i = 0;
            vring_packed_desc_read(vdev, &desc, desc_cache, i, false);
        }

        do {
            /* If we've got too many, that implies a descriptor loop. */
            if (++num_bufs > max) {
                virtio_error(vdev, "Looped descriptor");
                goto err;
            }

            if (desc.flags & VRING_DESC_F_WRITE) {
                in_total += desc.len;
            } else {
                out_total += desc.len;
            }
            if (in_total >= max_in_bytes && out_total >= max_out_bytes) {
                goto done;
            }

            rc = virtqueue_packed_read_next_desc(vq, &desc, desc_cache, max,
                                                 &i, desc_cache ==
                                                 &indirect_desc_cache);
        } while (rc == VIRTQUEUE_READ_DESC_MORE);

        if (desc_cache == &indirect_desc_cache) {
            address_space_cache_destroy(&indirect_desc_cache);
            total_bufs++;
            idx++;
        } else {
            idx += num_bufs - total_bufs;
            total_bufs = num_bufs;
        }

        if (idx >= vq->vring.num) {
            idx -= vq->vring.num;
            wrap_counter ^= 1;
        }
    }

    /* Record the index and wrap counter for a kick we want */
    vq->shadow_avail_idx = idx;
    vq->shadow_avail_wrap_counter = wrap_counter;
done:
    address_space_cache_destroy(&indirect_desc_cache);
    if (in_bytes) {
        *in_bytes = in_total;
    }
    if (out_bytes) {
        *out_bytes = out_total;
    }
    return;

err:
    in_total = out_total = 0;
    goto done;
}

void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes,
                               unsigned int *out_bytes,
                               unsigned max_in_bytes, unsigned max_out_bytes)
{
    uint16_t desc_size;
    VRingMemoryRegionCaches *caches;

    RCU_READ_LOCK_GUARD();

    if (unlikely(!vq->vring.desc)) {
        goto err;
    }

    caches = vring_get_region_caches(vq);
    if (!caches) {
        goto err;
    }

    desc_size = virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED) ?
                                sizeof(VRingPackedDesc) : sizeof(VRingDesc);
    if (caches->desc.len < vq->vring.num * desc_size) {
        virtio_error(vq->vdev, "Cannot map descriptor ring");
        goto err;
    }

    if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) {
        virtqueue_packed_get_avail_bytes(vq, in_bytes, out_bytes,
                                         max_in_bytes, max_out_bytes,
                                         caches);
    } else {
        virtqueue_split_get_avail_bytes(vq, in_bytes, out_bytes,
                                        max_in_bytes, max_out_bytes,
                                        caches);
    }

    return;
err:
    if (in_bytes) {
        *in_bytes = 0;
    }
    if (out_bytes) {
        *out_bytes = 0;
    }
}

int virtqueue_avail_bytes(VirtQueue *vq, unsigned int in_bytes,
                          unsigned int out_bytes)
{
    unsigned int in_total, out_total;

    virtqueue_get_avail_bytes(vq, &in_total, &out_total, in_bytes, out_bytes);
    return in_bytes <= in_total && out_bytes <= out_total;
}

static bool virtqueue_map_desc(VirtIODevice *vdev, unsigned int *p_num_sg,
                               hwaddr *addr, struct iovec *iov,
                               unsigned int max_num_sg, bool is_write,
                               hwaddr pa, size_t sz)
{
    bool ok = false;
    unsigned num_sg = *p_num_sg;
    assert(num_sg <= max_num_sg);

    if (!sz) {
        virtio_error(vdev, "virtio: zero sized buffers are not allowed");
        goto out;
    }

    while (sz) {
        hwaddr len = sz;

        if (num_sg == max_num_sg) {
            virtio_error(vdev, "virtio: too many write descriptors in "
                               "indirect table");
            goto out;
        }

        iov[num_sg].iov_base = dma_memory_map(vdev->dma_as, pa, &len,
                                              is_write ?
                                              DMA_DIRECTION_FROM_DEVICE :
                                              DMA_DIRECTION_TO_DEVICE,
                                              MEMTXATTRS_UNSPECIFIED);
        if (!iov[num_sg].iov_base) {
            virtio_error(vdev, "virtio: bogus descriptor or out of resources");
            goto out;
        }

        iov[num_sg].iov_len = len;
        addr[num_sg] = pa;

        sz -= len;
        pa += len;
        num_sg++;
    }
    ok = true;

out:
    *p_num_sg = num_sg;
    return ok;
}

/* Only used by error code paths before we have a VirtQueueElement (therefore
 * virtqueue_unmap_sg() can't be used).  Assumes buffers weren't written to
 * yet.
 */
static void virtqueue_undo_map_desc(unsigned int out_num, unsigned int in_num,
                                    struct iovec *iov)
{
    unsigned int i;

    for (i = 0; i < out_num + in_num; i++) {
        int is_write = i >= out_num;

        cpu_physical_memory_unmap(iov->iov_base, iov->iov_len, is_write, 0);
        iov++;
    }
}

static void virtqueue_map_iovec(VirtIODevice *vdev, struct iovec *sg,
                                hwaddr *addr, unsigned int num_sg,
                                bool is_write)
{
    unsigned int i;
    hwaddr len;

    for (i = 0; i < num_sg; i++) {
        len = sg[i].iov_len;
        sg[i].iov_base = dma_memory_map(vdev->dma_as,
                                        addr[i], &len, is_write ?
                                        DMA_DIRECTION_FROM_DEVICE :
                                        DMA_DIRECTION_TO_DEVICE,
                                        MEMTXATTRS_UNSPECIFIED);
        if (!sg[i].iov_base) {
            error_report("virtio: error trying to map MMIO memory");
            exit(1);
        }
        if (len != sg[i].iov_len) {
            error_report("virtio: unexpected memory split");
            exit(1);
        }
    }
}

void virtqueue_map(VirtIODevice *vdev, VirtQueueElement *elem)
{
    virtqueue_map_iovec(vdev, elem->in_sg, elem->in_addr, elem->in_num, true);
    virtqueue_map_iovec(vdev, elem->out_sg, elem->out_addr, elem->out_num,
                                                                        false);
}

static void *virtqueue_alloc_element(size_t sz, unsigned out_num, unsigned in_num)
{
    VirtQueueElement *elem;
    size_t in_addr_ofs = QEMU_ALIGN_UP(sz, __alignof__(elem->in_addr[0]));
    size_t out_addr_ofs = in_addr_ofs + in_num * sizeof(elem->in_addr[0]);
    size_t out_addr_end = out_addr_ofs + out_num * sizeof(elem->out_addr[0]);
    size_t in_sg_ofs = QEMU_ALIGN_UP(out_addr_end, __alignof__(elem->in_sg[0]));
    size_t out_sg_ofs = in_sg_ofs + in_num * sizeof(elem->in_sg[0]);
    size_t out_sg_end = out_sg_ofs + out_num * sizeof(elem->out_sg[0]);

    assert(sz >= sizeof(VirtQueueElement));
    elem = g_malloc(out_sg_end);
    trace_virtqueue_alloc_element(elem, sz, in_num, out_num);
    elem->out_num = out_num;
    elem->in_num = in_num;
    elem->in_addr = (void *)elem + in_addr_ofs;
    elem->out_addr = (void *)elem + out_addr_ofs;
    elem->in_sg = (void *)elem + in_sg_ofs;
    elem->out_sg = (void *)elem + out_sg_ofs;
    return elem;
}

static void *virtqueue_split_pop(VirtQueue *vq, size_t sz)
{
    unsigned int i, head, max;
    VRingMemoryRegionCaches *caches;
    MemoryRegionCache indirect_desc_cache = MEMORY_REGION_CACHE_INVALID;
    MemoryRegionCache *desc_cache;
    int64_t len;
    VirtIODevice *vdev = vq->vdev;
    VirtQueueElement *elem = NULL;
    unsigned out_num, in_num, elem_entries;
    hwaddr addr[VIRTQUEUE_MAX_SIZE];
    struct iovec iov[VIRTQUEUE_MAX_SIZE];
    VRingDesc desc;
    int rc;

    RCU_READ_LOCK_GUARD();
    if (virtio_queue_empty_rcu(vq)) {
        goto done;
    }
    /* Needed after virtio_queue_empty(), see comment in
     * virtqueue_num_heads(). */
    smp_rmb();

    /* When we start there are none of either input nor output. */
    out_num = in_num = elem_entries = 0;

    max = vq->vring.num;

    if (vq->inuse >= vq->vring.num) {
        virtio_error(vdev, "Virtqueue size exceeded");
        goto done;
    }

    if (!virtqueue_get_head(vq, vq->last_avail_idx++, &head)) {
        goto done;
    }

    if (virtio_vdev_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX)) {
        vring_set_avail_event(vq, vq->last_avail_idx);
    }

    i = head;

    caches = vring_get_region_caches(vq);
    if (!caches) {
        virtio_error(vdev, "Region caches not initialized");
        goto done;
    }

    if (caches->desc.len < max * sizeof(VRingDesc)) {
        virtio_error(vdev, "Cannot map descriptor ring");
        goto done;
    }

    desc_cache = &caches->desc;
    vring_split_desc_read(vdev, &desc, desc_cache, i);
    if (desc.flags & VRING_DESC_F_INDIRECT) {
        if (!desc.len || (desc.len % sizeof(VRingDesc))) {
            virtio_error(vdev, "Invalid size for indirect buffer table");
            goto done;
        }

        /* loop over the indirect descriptor table */
        len = address_space_cache_init(&indirect_desc_cache, vdev->dma_as,
                                       desc.addr, desc.len, false);
        desc_cache = &indirect_desc_cache;
        if (len < desc.len) {
            virtio_error(vdev, "Cannot map indirect buffer");
            goto done;
        }

        max = desc.len / sizeof(VRingDesc);
        i = 0;
        vring_split_desc_read(vdev, &desc, desc_cache, i);
    }

    /* Collect all the descriptors */
    do {
        bool map_ok;

        if (desc.flags & VRING_DESC_F_WRITE) {
            map_ok = virtqueue_map_desc(vdev, &in_num, addr + out_num,
                                        iov + out_num,
                                        VIRTQUEUE_MAX_SIZE - out_num, true,
                                        desc.addr, desc.len);
        } else {
            if (in_num) {
                virtio_error(vdev, "Incorrect order for descriptors");
                goto err_undo_map;
            }
            map_ok = virtqueue_map_desc(vdev, &out_num, addr, iov,
                                        VIRTQUEUE_MAX_SIZE, false,
                                        desc.addr, desc.len);
        }
        if (!map_ok) {
            goto err_undo_map;
        }

        /* If we've got too many, that implies a descriptor loop. */
        if (++elem_entries > max) {
            virtio_error(vdev, "Looped descriptor");
            goto err_undo_map;
        }

        rc = virtqueue_split_read_next_desc(vdev, &desc, desc_cache, max, &i);

    } while (rc == VIRTQUEUE_READ_DESC_MORE);

    if (rc == VIRTQUEUE_READ_DESC_ERROR) {
        goto err_undo_map;
    }

    /* Now copy what we have collected and mapped */
    elem = virtqueue_alloc_element(sz, out_num, in_num);
    elem->index = head;
    elem->ndescs = 1;
    for (i = 0; i < out_num; i++) {
        elem->out_addr[i] = addr[i];
        elem->out_sg[i] = iov[i];
    }
    for (i = 0; i < in_num; i++) {
        elem->in_addr[i] = addr[out_num + i];
        elem->in_sg[i] = iov[out_num + i];
    }

    vq->inuse++;

    trace_virtqueue_pop(vq, elem, elem->in_num, elem->out_num);
done:
    address_space_cache_destroy(&indirect_desc_cache);

    return elem;

err_undo_map:
    virtqueue_undo_map_desc(out_num, in_num, iov);
    goto done;
}

static void *virtqueue_packed_pop(VirtQueue *vq, size_t sz)
{
    unsigned int i, max;
    VRingMemoryRegionCaches *caches;
    MemoryRegionCache indirect_desc_cache = MEMORY_REGION_CACHE_INVALID;
    MemoryRegionCache *desc_cache;
    int64_t len;
    VirtIODevice *vdev = vq->vdev;
    VirtQueueElement *elem = NULL;
    unsigned out_num, in_num, elem_entries;
    hwaddr addr[VIRTQUEUE_MAX_SIZE];
    struct iovec iov[VIRTQUEUE_MAX_SIZE];
    VRingPackedDesc desc;
    uint16_t id;
    int rc;

    RCU_READ_LOCK_GUARD();
    if (virtio_queue_packed_empty_rcu(vq)) {
        goto done;
    }

    /* When we start there are none of either input nor output. */
    out_num = in_num = elem_entries = 0;

    max = vq->vring.num;

    if (vq->inuse >= vq->vring.num) {
        virtio_error(vdev, "Virtqueue size exceeded");
        goto done;
    }

    i = vq->last_avail_idx;

    caches = vring_get_region_caches(vq);
    if (!caches) {
        virtio_error(vdev, "Region caches not initialized");
        goto done;
    }

    if (caches->desc.len < max * sizeof(VRingDesc)) {
        virtio_error(vdev, "Cannot map descriptor ring");
        goto done;
    }

    desc_cache = &caches->desc;
    vring_packed_desc_read(vdev, &desc, desc_cache, i, true);
    id = desc.id;
    if (desc.flags & VRING_DESC_F_INDIRECT) {
        if (desc.len % sizeof(VRingPackedDesc)) {
            virtio_error(vdev, "Invalid size for indirect buffer table");
            goto done;
        }

        /* loop over the indirect descriptor table */
        len = address_space_cache_init(&indirect_desc_cache, vdev->dma_as,
                                       desc.addr, desc.len, false);
        desc_cache = &indirect_desc_cache;
        if (len < desc.len) {
            virtio_error(vdev, "Cannot map indirect buffer");
            goto done;
        }

        max = desc.len / sizeof(VRingPackedDesc);
        i = 0;
        vring_packed_desc_read(vdev, &desc, desc_cache, i, false);
    }

    /* Collect all the descriptors */
    do {
        bool map_ok;

        if (desc.flags & VRING_DESC_F_WRITE) {
            map_ok = virtqueue_map_desc(vdev, &in_num, addr + out_num,
                                        iov + out_num,
                                        VIRTQUEUE_MAX_SIZE - out_num, true,
                                        desc.addr, desc.len);
        } else {
            if (in_num) {
                virtio_error(vdev, "Incorrect order for descriptors");
                goto err_undo_map;
            }
            map_ok = virtqueue_map_desc(vdev, &out_num, addr, iov,
                                        VIRTQUEUE_MAX_SIZE, false,
                                        desc.addr, desc.len);
        }
        if (!map_ok) {
            goto err_undo_map;
        }

        /* If we've got too many, that implies a descriptor loop. */
        if (++elem_entries > max) {
            virtio_error(vdev, "Looped descriptor");
            goto err_undo_map;
        }

        rc = virtqueue_packed_read_next_desc(vq, &desc, desc_cache, max, &i,
                                             desc_cache ==
                                             &indirect_desc_cache);
    } while (rc == VIRTQUEUE_READ_DESC_MORE);

    /* Now copy what we have collected and mapped */
    elem = virtqueue_alloc_element(sz, out_num, in_num);
    for (i = 0; i < out_num; i++) {
        elem->out_addr[i] = addr[i];
        elem->out_sg[i] = iov[i];
    }
    for (i = 0; i < in_num; i++) {
        elem->in_addr[i] = addr[out_num + i];
        elem->in_sg[i] = iov[out_num + i];
    }

    elem->index = id;
    elem->ndescs = (desc_cache == &indirect_desc_cache) ? 1 : elem_entries;
    vq->last_avail_idx += elem->ndescs;
    vq->inuse += elem->ndescs;

    if (vq->last_avail_idx >= vq->vring.num) {
        vq->last_avail_idx -= vq->vring.num;
        vq->last_avail_wrap_counter ^= 1;
    }

    vq->shadow_avail_idx = vq->last_avail_idx;
    vq->shadow_avail_wrap_counter = vq->last_avail_wrap_counter;

    trace_virtqueue_pop(vq, elem, elem->in_num, elem->out_num);
done:
    address_space_cache_destroy(&indirect_desc_cache);

    return elem;

err_undo_map:
    virtqueue_undo_map_desc(out_num, in_num, iov);
    goto done;
}

void *virtqueue_pop(VirtQueue *vq, size_t sz)
{
    if (virtio_device_disabled(vq->vdev)) {
        return NULL;
    }

    if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) {
        return virtqueue_packed_pop(vq, sz);
    } else {
        return virtqueue_split_pop(vq, sz);
    }
}

static unsigned int virtqueue_packed_drop_all(VirtQueue *vq)
{
    VRingMemoryRegionCaches *caches;
    MemoryRegionCache *desc_cache;
    unsigned int dropped = 0;
    VirtQueueElement elem = {};
    VirtIODevice *vdev = vq->vdev;
    VRingPackedDesc desc;

    RCU_READ_LOCK_GUARD();

    caches = vring_get_region_caches(vq);
    if (!caches) {
        return 0;
    }

    desc_cache = &caches->desc;

    virtio_queue_set_notification(vq, 0);

    while (vq->inuse < vq->vring.num) {
        unsigned int idx = vq->last_avail_idx;
        /*
         * works similar to virtqueue_pop but does not map buffers
         * and does not allocate any memory.
         */
        vring_packed_desc_read(vdev, &desc, desc_cache,
                               vq->last_avail_idx , true);
        if (!is_desc_avail(desc.flags, vq->last_avail_wrap_counter)) {
            break;
        }
        elem.index = desc.id;
        elem.ndescs = 1;
        while (virtqueue_packed_read_next_desc(vq, &desc, desc_cache,
                                               vq->vring.num, &idx, false)) {
            ++elem.ndescs;
        }
        /*
         * immediately push the element, nothing to unmap
         * as both in_num and out_num are set to 0.
         */
        virtqueue_push(vq, &elem, 0);
        dropped++;
        vq->last_avail_idx += elem.ndescs;
        if (vq->last_avail_idx >= vq->vring.num) {
            vq->last_avail_idx -= vq->vring.num;
            vq->last_avail_wrap_counter ^= 1;
        }
    }

    return dropped;
}

static unsigned int virtqueue_split_drop_all(VirtQueue *vq)
{
    unsigned int dropped = 0;
    VirtQueueElement elem = {};
    VirtIODevice *vdev = vq->vdev;
    bool fEventIdx = virtio_vdev_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);

    while (!virtio_queue_empty(vq) && vq->inuse < vq->vring.num) {
        /* works similar to virtqueue_pop but does not map buffers
        * and does not allocate any memory */
        smp_rmb();
        if (!virtqueue_get_head(vq, vq->last_avail_idx, &elem.index)) {
            break;
        }
        vq->inuse++;
        vq->last_avail_idx++;
        if (fEventIdx) {
            vring_set_avail_event(vq, vq->last_avail_idx);
        }
        /* immediately push the element, nothing to unmap
         * as both in_num and out_num are set to 0 */
        virtqueue_push(vq, &elem, 0);
        dropped++;
    }

    return dropped;
}

/* virtqueue_drop_all:
 * @vq: The #VirtQueue
 * Drops all queued buffers and indicates them to the guest
 * as if they are done. Useful when buffers can not be
 * processed but must be returned to the guest.
 */
unsigned int virtqueue_drop_all(VirtQueue *vq)
{
    struct VirtIODevice *vdev = vq->vdev;

    if (virtio_device_disabled(vq->vdev)) {
        return 0;
    }

    if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
        return virtqueue_packed_drop_all(vq);
    } else {
        return virtqueue_split_drop_all(vq);
    }
}

/* Reading and writing a structure directly to QEMUFile is *awful*, but
 * it is what QEMU has always done by mistake.  We can change it sooner
 * or later by bumping the version number of the affected vm states.
 * In the meanwhile, since the in-memory layout of VirtQueueElement
 * has changed, we need to marshal to and from the layout that was
 * used before the change.
 */
typedef struct VirtQueueElementOld {
    unsigned int index;
    unsigned int out_num;
    unsigned int in_num;
    hwaddr in_addr[VIRTQUEUE_MAX_SIZE];
    hwaddr out_addr[VIRTQUEUE_MAX_SIZE];
    struct iovec in_sg[VIRTQUEUE_MAX_SIZE];
    struct iovec out_sg[VIRTQUEUE_MAX_SIZE];
} VirtQueueElementOld;

void *qemu_get_virtqueue_element(VirtIODevice *vdev, QEMUFile *f, size_t sz)
{
    VirtQueueElement *elem;
    VirtQueueElementOld data;
    int i;

    qemu_get_buffer(f, (uint8_t *)&data, sizeof(VirtQueueElementOld));

    /* TODO: teach all callers that this can fail, and return failure instead
     * of asserting here.
     * This is just one thing (there are probably more) that must be
     * fixed before we can allow NDEBUG compilation.
     */
    assert(ARRAY_SIZE(data.in_addr) >= data.in_num);
    assert(ARRAY_SIZE(data.out_addr) >= data.out_num);

    elem = virtqueue_alloc_element(sz, data.out_num, data.in_num);
    elem->index = data.index;

    for (i = 0; i < elem->in_num; i++) {
        elem->in_addr[i] = data.in_addr[i];
    }

    for (i = 0; i < elem->out_num; i++) {
        elem->out_addr[i] = data.out_addr[i];
    }

    for (i = 0; i < elem->in_num; i++) {
        /* Base is overwritten by virtqueue_map.  */
        elem->in_sg[i].iov_base = 0;
        elem->in_sg[i].iov_len = data.in_sg[i].iov_len;
    }

    for (i = 0; i < elem->out_num; i++) {
        /* Base is overwritten by virtqueue_map.  */
        elem->out_sg[i].iov_base = 0;
        elem->out_sg[i].iov_len = data.out_sg[i].iov_len;
    }

    if (virtio_host_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
        qemu_get_be32s(f, &elem->ndescs);
    }

    virtqueue_map(vdev, elem);
    return elem;
}

void qemu_put_virtqueue_element(VirtIODevice *vdev, QEMUFile *f,
                                VirtQueueElement *elem)
{
    VirtQueueElementOld data;
    int i;

    memset(&data, 0, sizeof(data));
    data.index = elem->index;
    data.in_num = elem->in_num;
    data.out_num = elem->out_num;

    for (i = 0; i < elem->in_num; i++) {
        data.in_addr[i] = elem->in_addr[i];
    }

    for (i = 0; i < elem->out_num; i++) {
        data.out_addr[i] = elem->out_addr[i];
    }

    for (i = 0; i < elem->in_num; i++) {
        /* Base is overwritten by virtqueue_map when loading.  Do not
         * save it, as it would leak the QEMU address space layout.  */
        data.in_sg[i].iov_len = elem->in_sg[i].iov_len;
    }

    for (i = 0; i < elem->out_num; i++) {
        /* Do not save iov_base as above.  */
        data.out_sg[i].iov_len = elem->out_sg[i].iov_len;
    }

    if (virtio_host_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
        qemu_put_be32s(f, &elem->ndescs);
    }

    qemu_put_buffer(f, (uint8_t *)&data, sizeof(VirtQueueElementOld));
}

/* virtio device */
static void virtio_notify_vector(VirtIODevice *vdev, uint16_t vector)
{
    BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);

    if (virtio_device_disabled(vdev)) {
        return;
    }

    if (k->notify) {
        k->notify(qbus->parent, vector);
    }
}

void virtio_update_irq(VirtIODevice *vdev)
{
    virtio_notify_vector(vdev, VIRTIO_NO_VECTOR);
}

static int virtio_validate_features(VirtIODevice *vdev)
{
    VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);

    if (virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM) &&
        !virtio_vdev_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM)) {
        return -EFAULT;
    }

    if (k->validate_features) {
        return k->validate_features(vdev);
    } else {
        return 0;
    }
}

int virtio_set_status(VirtIODevice *vdev, uint8_t val)
{
    VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
    trace_virtio_set_status(vdev, val);

    if (virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) {
        if (!(vdev->status & VIRTIO_CONFIG_S_FEATURES_OK) &&
            val & VIRTIO_CONFIG_S_FEATURES_OK) {
            int ret = virtio_validate_features(vdev);

            if (ret) {
                return ret;
            }
        }
    }

    if ((vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) !=
        (val & VIRTIO_CONFIG_S_DRIVER_OK)) {
        virtio_set_started(vdev, val & VIRTIO_CONFIG_S_DRIVER_OK);
    }

    if (k->set_status) {
        k->set_status(vdev, val);
    }
    vdev->status = val;

    return 0;
}

static enum virtio_device_endian virtio_default_endian(void)
{
    if (target_words_bigendian()) {
        return VIRTIO_DEVICE_ENDIAN_BIG;
    } else {
        return VIRTIO_DEVICE_ENDIAN_LITTLE;
    }
}

static enum virtio_device_endian virtio_current_cpu_endian(void)
{
    if (cpu_virtio_is_big_endian(current_cpu)) {
        return VIRTIO_DEVICE_ENDIAN_BIG;
    } else {
        return VIRTIO_DEVICE_ENDIAN_LITTLE;
    }
}

static void __virtio_queue_reset(VirtIODevice *vdev, uint32_t i)
{
    vdev->vq[i].vring.desc = 0;
    vdev->vq[i].vring.avail = 0;
    vdev->vq[i].vring.used = 0;
    vdev->vq[i].last_avail_idx = 0;
    vdev->vq[i].shadow_avail_idx = 0;
    vdev->vq[i].used_idx = 0;
    vdev->vq[i].last_avail_wrap_counter = true;
    vdev->vq[i].shadow_avail_wrap_counter = true;
    vdev->vq[i].used_wrap_counter = true;
    virtio_queue_set_vector(vdev, i, VIRTIO_NO_VECTOR);
    vdev->vq[i].signalled_used = 0;
    vdev->vq[i].signalled_used_valid = false;
    vdev->vq[i].notification = true;
    vdev->vq[i].vring.num = vdev->vq[i].vring.num_default;
    vdev->vq[i].inuse = 0;
    virtio_virtqueue_reset_region_cache(&vdev->vq[i]);
}

void virtio_queue_reset(VirtIODevice *vdev, uint32_t queue_index)
{
    VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);

    if (k->queue_reset) {
        k->queue_reset(vdev, queue_index);
    }

    __virtio_queue_reset(vdev, queue_index);
}

void virtio_queue_enable(VirtIODevice *vdev, uint32_t queue_index)
{
    VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);

    /*
     * TODO: Seabios is currently out of spec and triggering this error.
     * So this needs to be fixed in Seabios, then this can
     * be re-enabled for new machine types only, and also after
     * being converted to LOG_GUEST_ERROR.
     *
    if (!virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) {
        error_report("queue_enable is only suppported in devices of virtio "
                     "1.0 or later.");
    }
    */

    if (k->queue_enable) {
        k->queue_enable(vdev, queue_index);
    }
}

void virtio_reset(void *opaque)
{
    VirtIODevice *vdev = opaque;
    VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
    int i;

    virtio_set_status(vdev, 0);
    if (current_cpu) {
        /* Guest initiated reset */
        vdev->device_endian = virtio_current_cpu_endian();
    } else {
        /* System reset */
        vdev->device_endian = virtio_default_endian();
    }

    if (k->reset) {
        k->reset(vdev);
    }

    vdev->start_on_kick = false;
    vdev->started = false;
    vdev->broken = false;
    vdev->guest_features = 0;
    vdev->queue_sel = 0;
    vdev->status = 0;
    vdev->disabled = false;
    qatomic_set(&vdev->isr, 0);
    vdev->config_vector = VIRTIO_NO_VECTOR;
    virtio_notify_vector(vdev, vdev->config_vector);

    for(i = 0; i < VIRTIO_QUEUE_MAX; i++) {
        __virtio_queue_reset(vdev, i);
    }
}

uint32_t virtio_config_readb(VirtIODevice *vdev, uint32_t addr)
{
    VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
    uint8_t val;

    if (addr + sizeof(val) > vdev->config_len) {
        return (uint32_t)-1;
    }

    k->get_config(vdev, vdev->config);

    val = ldub_p(vdev->config + addr);
    return val;
}

uint32_t virtio_config_readw(VirtIODevice *vdev, uint32_t addr)
{
    VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
    uint16_t val;

    if (addr + sizeof(val) > vdev->config_len) {
        return (uint32_t)-1;
    }

    k->get_config(vdev, vdev->config);

    val = lduw_p(vdev->config + addr);
    return val;
}

uint32_t virtio_config_readl(VirtIODevice *vdev, uint32_t addr)
{
    VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
    uint32_t val;

    if (addr + sizeof(val) > vdev->config_len) {
        return (uint32_t)-1;
    }

    k->get_config(vdev, vdev->config);

    val = ldl_p(vdev->config + addr);
    return val;
}

void virtio_config_writeb(VirtIODevice *vdev, uint32_t addr, uint32_t data)
{
    VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
    uint8_t val = data;

    if (addr + sizeof(val) > vdev->config_len) {
        return;
    }

    stb_p(vdev->config + addr, val);

    if (k->set_config) {
        k->set_config(vdev, vdev->config);
    }
}

void virtio_config_writew(VirtIODevice *vdev, uint32_t addr, uint32_t data)
{
    VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
    uint16_t val = data;

    if (addr + sizeof(val) > vdev->config_len) {
        return;
    }

    stw_p(vdev->config + addr, val);

    if (k->set_config) {
        k->set_config(vdev, vdev->config);
    }
}

void virtio_config_writel(VirtIODevice *vdev, uint32_t addr, uint32_t data)
{
    VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
    uint32_t val = data;

    if (addr + sizeof(val) > vdev->config_len) {
        return;
    }

    stl_p(vdev->config + addr, val);

    if (k->set_config) {
        k->set_config(vdev, vdev->config);
    }
}

uint32_t virtio_config_modern_readb(VirtIODevice *vdev, uint32_t addr)
{
    VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
    uint8_t val;

    if (addr + sizeof(val) > vdev->config_len) {
        return (uint32_t)-1;
    }

    k->get_config(vdev, vdev->config);

    val = ldub_p(vdev->config + addr);
    return val;
}

uint32_t virtio_config_modern_readw(VirtIODevice *vdev, uint32_t addr)
{
    VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
    uint16_t val;

    if (addr + sizeof(val) > vdev->config_len) {
        return (uint32_t)-1;
    }

    k->get_config(vdev, vdev->config);

    val = lduw_le_p(vdev->config + addr);
    return val;
}

uint32_t virtio_config_modern_readl(VirtIODevice *vdev, uint32_t addr)
{
    VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
    uint32_t val;

    if (addr + sizeof(val) > vdev->config_len) {
        return (uint32_t)-1;
    }

    k->get_config(vdev, vdev->config);

    val = ldl_le_p(vdev->config + addr);
    return val;
}

void virtio_config_modern_writeb(VirtIODevice *vdev,
                                 uint32_t addr, uint32_t data)
{
    VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
    uint8_t val = data;

    if (addr + sizeof(val) > vdev->config_len) {
        return;
    }

    stb_p(vdev->config + addr, val);

    if (k->set_config) {
        k->set_config(vdev, vdev->config);
    }
}

void virtio_config_modern_writew(VirtIODevice *vdev,
                                 uint32_t addr, uint32_t data)
{
    VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
    uint16_t val = data;

    if (addr + sizeof(val) > vdev->config_len) {
        return;
    }

    stw_le_p(vdev->config + addr, val);

    if (k->set_config) {
        k->set_config(vdev, vdev->config);
    }
}

void virtio_config_modern_writel(VirtIODevice *vdev,
                                 uint32_t addr, uint32_t data)
{
    VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
    uint32_t val = data;

    if (addr + sizeof(val) > vdev->config_len) {
        return;
    }

    stl_le_p(vdev->config + addr, val);

    if (k->set_config) {
        k->set_config(vdev, vdev->config);
    }
}

void virtio_queue_set_addr(VirtIODevice *vdev, int n, hwaddr addr)
{
    if (!vdev->vq[n].vring.num) {
        return;
    }
    vdev->vq[n].vring.desc = addr;
    virtio_queue_update_rings(vdev, n);
}

hwaddr virtio_queue_get_addr(VirtIODevice *vdev, int n)
{
    return vdev->vq[n].vring.desc;
}

void virtio_queue_set_rings(VirtIODevice *vdev, int n, hwaddr desc,
                            hwaddr avail, hwaddr used)
{
    if (!vdev->vq[n].vring.num) {
        return;
    }
    vdev->vq[n].vring.desc = desc;
    vdev->vq[n].vring.avail = avail;
    vdev->vq[n].vring.used = used;
    virtio_init_region_cache(vdev, n);
}

void virtio_queue_set_num(VirtIODevice *vdev, int n, int num)
{
    /* Don't allow guest to flip queue between existent and
     * nonexistent states, or to set it to an invalid size.
     */
    if (!!num != !!vdev->vq[n].vring.num ||
        num > VIRTQUEUE_MAX_SIZE ||
        num < 0) {
        return;
    }
    vdev->vq[n].vring.num = num;
}

VirtQueue *virtio_vector_first_queue(VirtIODevice *vdev, uint16_t vector)
{
    return QLIST_FIRST(&vdev->vector_queues[vector]);
}

VirtQueue *virtio_vector_next_queue(VirtQueue *vq)
{
    return QLIST_NEXT(vq, node);
}

int virtio_queue_get_num(VirtIODevice *vdev, int n)
{
    return vdev->vq[n].vring.num;
}

int virtio_queue_get_max_num(VirtIODevice *vdev, int n)
{
    return vdev->vq[n].vring.num_default;
}

int virtio_get_num_queues(VirtIODevice *vdev)
{
    int i;

    for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
        if (!virtio_queue_get_num(vdev, i)) {
            break;
        }
    }

    return i;
}

void virtio_queue_set_align(VirtIODevice *vdev, int n, int align)
{
    BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);

    /* virtio-1 compliant devices cannot change the alignment */
    if (virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) {
        error_report("tried to modify queue alignment for virtio-1 device");
        return;
    }
    /* Check that the transport told us it was going to do this
     * (so a buggy transport will immediately assert rather than
     * silently failing to migrate this state)
     */
    assert(k->has_variable_vring_alignment);

    if (align) {
        vdev->vq[n].vring.align = align;
        virtio_queue_update_rings(vdev, n);
    }
}

static void virtio_queue_notify_vq(VirtQueue *vq)
{
    if (vq->vring.desc && vq->handle_output) {
        VirtIODevice *vdev = vq->vdev;

        if (unlikely(vdev->broken)) {
            return;
        }

        trace_virtio_queue_notify(vdev, vq - vdev->vq, vq);
        vq->handle_output(vdev, vq);

        if (unlikely(vdev->start_on_kick)) {
            virtio_set_started(vdev, true);
        }
    }
}

void virtio_queue_notify(VirtIODevice *vdev, int n)
{
    VirtQueue *vq = &vdev->vq[n];

    if (unlikely(!vq->vring.desc || vdev->broken)) {
        return;
    }

    trace_virtio_queue_notify(vdev, vq - vdev->vq, vq);
    if (vq->host_notifier_enabled) {
        event_notifier_set(&vq->host_notifier);
    } else if (vq->handle_output) {
        vq->handle_output(vdev, vq);

        if (unlikely(vdev->start_on_kick)) {
            virtio_set_started(vdev, true);
        }
    }
}

uint16_t virtio_queue_vector(VirtIODevice *vdev, int n)
{
    return n < VIRTIO_QUEUE_MAX ? vdev->vq[n].vector :
        VIRTIO_NO_VECTOR;
}

void virtio_queue_set_vector(VirtIODevice *vdev, int n, uint16_t vector)
{
    VirtQueue *vq = &vdev->vq[n];

    if (n < VIRTIO_QUEUE_MAX) {
        if (vdev->vector_queues &&
            vdev->vq[n].vector != VIRTIO_NO_VECTOR) {
            QLIST_REMOVE(vq, node);
        }
        vdev->vq[n].vector = vector;
        if (vdev->vector_queues &&
            vector != VIRTIO_NO_VECTOR) {
            QLIST_INSERT_HEAD(&vdev->vector_queues[vector], vq, node);
        }
    }
}

VirtQueue *virtio_add_queue(VirtIODevice *vdev, int queue_size,
                            VirtIOHandleOutput handle_output)
{
    int i;

    for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
        if (vdev->vq[i].vring.num == 0)
            break;
    }

    if (i == VIRTIO_QUEUE_MAX || queue_size > VIRTQUEUE_MAX_SIZE)
        abort();

    vdev->vq[i].vring.num = queue_size;
    vdev->vq[i].vring.num_default = queue_size;
    vdev->vq[i].vring.align = VIRTIO_PCI_VRING_ALIGN;
    vdev->vq[i].handle_output = handle_output;
    vdev->vq[i].used_elems = g_new0(VirtQueueElement, queue_size);

    return &vdev->vq[i];
}

void virtio_delete_queue(VirtQueue *vq)
{
    vq->vring.num = 0;
    vq->vring.num_default = 0;
    vq->handle_output = NULL;
    g_free(vq->used_elems);
    vq->used_elems = NULL;
    virtio_virtqueue_reset_region_cache(vq);
}

void virtio_del_queue(VirtIODevice *vdev, int n)
{
    if (n < 0 || n >= VIRTIO_QUEUE_MAX) {
        abort();
    }

    virtio_delete_queue(&vdev->vq[n]);
}

static void virtio_set_isr(VirtIODevice *vdev, int value)
{
    uint8_t old = qatomic_read(&vdev->isr);

    /* Do not write ISR if it does not change, so that its cacheline remains
     * shared in the common case where the guest does not read it.
     */
    if ((old & value) != value) {
        qatomic_or(&vdev->isr, value);
    }
}

/* Called within rcu_read_lock(). */
static bool virtio_split_should_notify(VirtIODevice *vdev, VirtQueue *vq)
{
    uint16_t old, new;
    bool v;
    /* We need to expose used array entries before checking used event. */
    smp_mb();
    /* Always notify when queue is empty (when feature acknowledge) */
    if (virtio_vdev_has_feature(vdev, VIRTIO_F_NOTIFY_ON_EMPTY) &&
        !vq->inuse && virtio_queue_empty(vq)) {
        return true;
    }

    if (!virtio_vdev_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX)) {
        return !(vring_avail_flags(vq) & VRING_AVAIL_F_NO_INTERRUPT);
    }

    v = vq->signalled_used_valid;
    vq->signalled_used_valid = true;
    old = vq->signalled_used;
    new = vq->signalled_used = vq->used_idx;
    return !v || vring_need_event(vring_get_used_event(vq), new, old);
}

static bool vring_packed_need_event(VirtQueue *vq, bool wrap,
                                    uint16_t off_wrap, uint16_t new,
                                    uint16_t old)
{
    int off = off_wrap & ~(1 << 15);

    if (wrap != off_wrap >> 15) {
        off -= vq->vring.num;
    }

    return vring_need_event(off, new, old);
}

/* Called within rcu_read_lock(). */
static bool virtio_packed_should_notify(VirtIODevice *vdev, VirtQueue *vq)
{
    VRingPackedDescEvent e;
    uint16_t old, new;
    bool v;
    VRingMemoryRegionCaches *caches;

    caches = vring_get_region_caches(vq);
    if (!caches) {
        return false;
    }