// SPDX-License-Identifier: GPL-2.0
/*
 * PCI Backend Operations - respond to PCI requests from Frontend
 *
 *   Author: Ryan Wilson <hap9@epoch.ncsc.mil>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#define dev_fmt pr_fmt

#include <linux/moduleparam.h>
#include <linux/wait.h>
#include <linux/bitops.h>
#include <xen/events.h>
#include <linux/sched.h>
#include "pciback.h"

static irqreturn_t xen_pcibk_guest_interrupt(int irq, void *dev_id);

/* Ensure a device is has the fake IRQ handler "turned on/off" and is
 * ready to be exported. This MUST be run after xen_pcibk_reset_device
 * which does the actual PCI device enable/disable.
 */
static void xen_pcibk_control_isr(struct pci_dev *dev, int reset)
{
        struct xen_pcibk_dev_data *dev_data;
        int rc;
        int enable = 0;

        dev_data = pci_get_drvdata(dev);
        if (!dev_data)
                return;

        /* We don't deal with bridges */
        if (dev->hdr_type != PCI_HEADER_TYPE_NORMAL)
                return;

        if (reset) {
                dev_data->enable_intx = 0;
                dev_data->ack_intr = 0;
        }
        enable =  dev_data->enable_intx;

        /* Asked to disable, but ISR isn't runnig */
        if (!enable && !dev_data->isr_on)
                return;

        /* Squirrel away the IRQs in the dev_data. We need this
         * b/c when device transitions to MSI, the dev->irq is
         * overwritten with the MSI vector.
         */
        if (enable)
                dev_data->irq = dev->irq;

        /*
         * SR-IOV devices in all use MSI-X and have no legacy
         * interrupts, so inhibit creating a fake IRQ handler for them.
         */
        if (dev_data->irq == 0)
                goto out;

        dev_dbg(&dev->dev, "%s: #%d %s %s%s %s-> %s\n",
                dev_data->irq_name,
                dev_data->irq,
                pci_is_enabled(dev) ? "on" : "off",
                dev->msi_enabled ? "MSI" : "",
                dev->msix_enabled ? "MSI/X" : "",
                dev_data->isr_on ? "enable" : "disable",
                enable ? "enable" : "disable");

        if (enable) {
                /*
                 * The MSI or MSI-X should not have an IRQ handler. Otherwise
                 * if the guest terminates we BUG_ON in free_msi_irqs.
                 */
                if (dev->msi_enabled || dev->msix_enabled)
                        goto out;

                rc = request_irq(dev_data->irq,
                                xen_pcibk_guest_interrupt, IRQF_SHARED,
                                dev_data->irq_name, dev);
                if (rc) {
                        dev_err(&dev->dev, "%s: failed to install fake IRQ " \
                                "handler for IRQ %d! (rc:%d)\n",
                                dev_data->irq_name, dev_data->irq, rc);
                        goto out;
                }
        } else {
                free_irq(dev_data->irq, dev);
                dev_data->irq = 0;
        }
        dev_data->isr_on = enable;
        dev_data->ack_intr = enable;
out:
        dev_dbg(&dev->dev, "%s: #%d %s %s%s %s\n",
                dev_data->irq_name,
                dev_data->irq,
                pci_is_enabled(dev) ? "on" : "off",
                dev->msi_enabled ? "MSI" : "",
                dev->msix_enabled ? "MSI/X" : "",
                enable ? (dev_data->isr_on ? "enabled" : "failed to enable") :
                        (dev_data->isr_on ? "failed to disable" : "disabled"));
}

/* Ensure a device is "turned off" and ready to be exported.
 * (Also see xen_pcibk_config_reset to ensure virtual configuration space is
 * ready to be re-exported)
 */
void xen_pcibk_reset_device(struct pci_dev *dev)
{
        u16 cmd;

        xen_pcibk_control_isr(dev, 1 /* reset device */);

        /* Disable devices (but not bridges) */
        if (dev->hdr_type == PCI_HEADER_TYPE_NORMAL) {
#ifdef CONFIG_PCI_MSI
                /* The guest could have been abruptly killed without
                 * disabling MSI/MSI-X interrupts.*/
                if (dev->msix_enabled)
                        pci_disable_msix(dev);
                if (dev->msi_enabled)
                        pci_disable_msi(dev);
#endif
                if (pci_is_enabled(dev))
                        pci_disable_device(dev);

                dev->is_busmaster = 0;
        } else {
                pci_read_config_word(dev, PCI_COMMAND, &cmd);
                if (cmd & (PCI_COMMAND_INVALIDATE)) {
                        cmd &= ~(PCI_COMMAND_INVALIDATE);
                        pci_write_config_word(dev, PCI_COMMAND, cmd);

                        dev->is_busmaster = 0;
                }
        }
}

#ifdef CONFIG_PCI_MSI
static
int xen_pcibk_enable_msi(struct xen_pcibk_device *pdev,
                         struct pci_dev *dev, struct xen_pci_op *op)
{
        struct xen_pcibk_dev_data *dev_data;
        int status;

        if (dev->msi_enabled)
                status = -EALREADY;
        else if (dev->msix_enabled)
                status = -ENXIO;
        else
                status = pci_enable_msi(dev);

        if (status) {
                dev_warn_ratelimited(&dev->dev, "error enabling MSI for guest %u: err %d\n",
                                     pdev->xdev->otherend_id, status);
                op->value = 0;
                return XEN_PCI_ERR_op_failed;
        }

        /* The value the guest needs is actually the IDT vector, not the
         * the local domain's IRQ number. */

        op->value = dev->irq ? xen_pirq_from_irq(dev->irq) : 0;

        dev_dbg(&dev->dev, "MSI: %d\n", op->value);

        dev_data = pci_get_drvdata(dev);
        if (dev_data)
                dev_data->ack_intr = 0;

        return 0;
}

static
int xen_pcibk_disable_msi(struct xen_pcibk_device *pdev,
                          struct pci_dev *dev, struct xen_pci_op *op)
{
        if (dev->msi_enabled) {
                struct xen_pcibk_dev_data *dev_data;

                pci_disable_msi(dev);

                dev_data = pci_get_drvdata(dev);
                if (dev_data)
                        dev_data->ack_intr = 1;
        }
        op->value = dev->irq ? xen_pirq_from_irq(dev->irq) : 0;

        dev_dbg(&dev->dev, "MSI: %d\n", op->value);

        return 0;
}

static
int xen_pcibk_enable_msix(struct xen_pcibk_device *pdev,
                          struct pci_dev *dev, struct xen_pci_op *op)
{
        struct xen_pcibk_dev_data *dev_data;
        int i, result;
        struct msix_entry *entries;
        u16 cmd;

        dev_dbg(&dev->dev, "enable MSI-X\n");

        if (op->value > SH_INFO_MAX_VEC)
                return -EINVAL;

        if (dev->msix_enabled)
                return -EALREADY;

        /*
         * PCI_COMMAND_MEMORY must be enabled, otherwise we may not be able
         * to access the BARs where the MSI-X entries reside.
         * But VF devices are unique in which the PF needs to be checked.
         */
        pci_read_config_word(pci_physfn(dev), PCI_COMMAND, &cmd);
        if (dev->msi_enabled || !(cmd & PCI_COMMAND_MEMORY))
                return -ENXIO;

        entries = kmalloc_array(op->value, sizeof(*entries), GFP_KERNEL);
        if (entries == NULL)
                return -ENOMEM;

        for (i = 0; i < op->value; i++) {
                entries[i].entry = op->msix_entries[i].entry;
                entries[i].vector = op->msix_entries[i].vector;
        }

        result = pci_enable_msix_exact(dev, entries, op->value);
        if (result == 0) {
                for (i = 0; i < op->value; i++) {
                        op->msix_entries[i].entry = entries[i].entry;
                        if (entries[i].vector) {
                                op->msix_entries[i].vector =
                                        xen_pirq_from_irq(entries[i].vector);
                                dev_dbg(&dev->dev, "MSI-X[%d]: %d\n", i,
                                        op->msix_entries[i].vector);
                        }
                }
        } else
                dev_warn_ratelimited(&dev->dev, "error enabling MSI-X for guest %u: err %d!\n",
                                     pdev->xdev->otherend_id, result);
        kfree(entries);

        op->value = result;
        dev_data = pci_get_drvdata(dev);
        if (dev_data)
                dev_data->ack_intr = 0;

        return result > 0 ? 0 : result;
}

static
int xen_pcibk_disable_msix(struct xen_pcibk_device *pdev,
                           struct pci_dev *dev, struct xen_pci_op *op)
{
        if (dev->msix_enabled) {
                struct xen_pcibk_dev_data *dev_data;

                pci_disable_msix(dev);

                dev_data = pci_get_drvdata(dev);
                if (dev_data)
                        dev_data->ack_intr = 1;
        }
        /*
         * SR-IOV devices (which don't have any legacy IRQ) have
         * an undefined IRQ value of zero.
         */
        op->value = dev->irq ? xen_pirq_from_irq(dev->irq) : 0;

        dev_dbg(&dev->dev, "MSI-X: %d\n", op->value);

        return 0;
}
#endif

static inline bool xen_pcibk_test_op_pending(struct xen_pcibk_device *pdev)
{
        return test_bit(_XEN_PCIF_active,
                        (unsigned long *)&pdev->sh_info->flags) &&
               !test_and_set_bit(_PDEVF_op_active, &pdev->flags);
}

/*
* Now the same evtchn is used for both pcifront conf_read_write request
* as well as pcie aer front end ack. We use a new work_queue to schedule
* xen_pcibk conf_read_write service for avoiding confict with aer_core
* do_recovery job which also use the system default work_queue
*/
static void xen_pcibk_test_and_schedule_op(struct xen_pcibk_device *pdev)
{
        bool eoi = true;

        /* Check that frontend is requesting an operation and that we are not
         * already processing a request */
        if (xen_pcibk_test_op_pending(pdev)) {
                schedule_work(&pdev->op_work);
                eoi = false;
        }
        /*_XEN_PCIB_active should have been cleared by pcifront. And also make
        sure xen_pcibk is waiting for ack by checking _PCIB_op_pending*/
        if (!test_bit(_XEN_PCIB_active, (unsigned long *)&pdev->sh_info->flags)
            && test_bit(_PCIB_op_pending, &pdev->flags)) {
                wake_up(&xen_pcibk_aer_wait_queue);
                eoi = false;
        }

        /* EOI if there was nothing to do. */
        if (eoi)
                xen_pcibk_lateeoi(pdev, XEN_EOI_FLAG_SPURIOUS);
}

/* Performing the configuration space reads/writes must not be done in atomic
 * context because some of the pci_* functions can sleep (mostly due to ACPI
 * use of semaphores). This function is intended to be called from a work
 * queue in process context taking a struct xen_pcibk_device as a parameter */

static void xen_pcibk_do_one_op(struct xen_pcibk_device *pdev)
{
        struct pci_dev *dev;
        struct xen_pcibk_dev_data *dev_data = NULL;
        struct xen_pci_op *op = &pdev->op;
        int test_intx = 0;
#ifdef CONFIG_PCI_MSI
        unsigned int nr = 0;
#endif

        *op = pdev->sh_info->op;
        barrier();
        dev = xen_pcibk_get_pci_dev(pdev, op->domain, op->bus, op->devfn);

        if (dev == NULL)
                op->err = XEN_PCI_ERR_dev_not_found;
        else {
                dev_data = pci_get_drvdata(dev);
                if (dev_data)
                        test_intx = dev_data->enable_intx;
                switch (op->cmd) {
                case XEN_PCI_OP_conf_read:
                        op->err = xen_pcibk_config_read(dev,
                                  op->offset, op->size, &op->value);
                        break;
                case XEN_PCI_OP_conf_write:
                        op->err = xen_pcibk_config_write(dev,
                                  op->offset, op->size, op->value);
                        break;
#ifdef CONFIG_PCI_MSI
                case XEN_PCI_OP_enable_msi:
                        op->err = xen_pcibk_enable_msi(pdev, dev, op);
                        break;
                case XEN_PCI_OP_disable_msi:
                        op->err = xen_pcibk_disable_msi(pdev, dev, op);
                        break;
                case XEN_PCI_OP_enable_msix:
                        nr = op->value;
                        op->err = xen_pcibk_enable_msix(pdev, dev, op);
                        break;
                case XEN_PCI_OP_disable_msix:
                        op->err = xen_pcibk_disable_msix(pdev, dev, op);
                        break;
#endif
                default:
                        op->err = XEN_PCI_ERR_not_implemented;
                        break;
                }
        }
        if (!op->err && dev && dev_data) {
                /* Transition detected */
                if ((dev_data->enable_intx != test_intx))
                        xen_pcibk_control_isr(dev, 0 /* no reset */);
        }
        pdev->sh_info->op.err = op->err;
        pdev->sh_info->op.value = op->value;
#ifdef CONFIG_PCI_MSI
        if (op->cmd == XEN_PCI_OP_enable_msix && op->err == 0) {
                unsigned int i;

                for (i = 0; i < nr; i++)
                        pdev->sh_info->op.msix_entries[i].vector =
                                op->msix_entries[i].vector;
        }
#endif
        /* Tell the driver domain that we're done. */
        wmb();
        clear_bit(_XEN_PCIF_active, (unsigned long *)&pdev->sh_info->flags);
        notify_remote_via_irq(pdev->evtchn_irq);

        /* Mark that we're done. */
        smp_mb__before_atomic(); /* /after/ clearing PCIF_active */
        clear_bit(_PDEVF_op_active, &pdev->flags);
        smp_mb__after_atomic(); /* /before/ final check for work */
}

void xen_pcibk_do_op(struct work_struct *data)
{
        struct xen_pcibk_device *pdev =
                container_of(data, struct xen_pcibk_device, op_work);

        do {
                xen_pcibk_do_one_op(pdev);
        } while (xen_pcibk_test_op_pending(pdev));

        xen_pcibk_lateeoi(pdev, 0);
}

irqreturn_t xen_pcibk_handle_event(int irq, void *dev_id)
{
        struct xen_pcibk_device *pdev = dev_id;
        bool eoi;

        /* IRQs might come in before pdev->evtchn_irq is written. */
        if (unlikely(pdev->evtchn_irq != irq))
                pdev->evtchn_irq = irq;

        eoi = test_and_set_bit(_EOI_pending, &pdev->flags);
        WARN(eoi, "IRQ while EOI pending\n");

        xen_pcibk_test_and_schedule_op(pdev);

        return IRQ_HANDLED;
}
static irqreturn_t xen_pcibk_guest_interrupt(int irq, void *dev_id)
{
        struct pci_dev *dev = (struct pci_dev *)dev_id;
        struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);

        if (dev_data->isr_on && dev_data->ack_intr) {
                dev_data->handled++;
                if ((dev_data->handled % 1000) == 0) {
                        if (xen_test_irq_shared(irq)) {
                                dev_info(&dev->dev, "%s IRQ line is not shared "
                                        "with other domains. Turning ISR off\n",
                                         dev_data->irq_name);
                                dev_data->ack_intr = 0;
                        }
                }
                return IRQ_HANDLED;
        }
        return IRQ_NONE;
}