// SPDX-License-Identifier: MIT License
/*
 * hypervisor.c
 *
 * Communication to/from hypervisor.
 *
 * Copyright (c) 2002-2003, K A Fraser
 * Copyright (c) 2005, Grzegorz Milos, gm281@cam.ac.uk,Intel Research Cambridge
 * Copyright (c) 2020, EPAM Systems Inc.
 */
#include <common.h>
#include <cpu_func.h>
#include <log.h>
#include <memalign.h>

#include <asm/io.h>
#include <asm/armv8/mmu.h>
#include <asm/xen/system.h>

#include <linux/bug.h>

#include <xen/hvm.h>
#include <xen/events.h>
#include <xen/gnttab.h>
#include <xen/xenbus.h>
#include <xen/interface/memory.h>

#define active_evtchns(cpu, sh, idx)    \
        ((sh)->evtchn_pending[idx] &    \
         ~(sh)->evtchn_mask[idx])

int in_callback;

/*
 * Shared page for communicating with the hypervisor.
 * Events flags go here, for example.
 */
struct shared_info *HYPERVISOR_shared_info;

static const char *param_name(int op)
{
#define PARAM(x)[HVM_PARAM_##x] = #x
        static const char *const names[] = {
                PARAM(CALLBACK_IRQ),
                PARAM(STORE_PFN),
                PARAM(STORE_EVTCHN),
                PARAM(PAE_ENABLED),
                PARAM(IOREQ_PFN),
                PARAM(VPT_ALIGN),
                PARAM(CONSOLE_PFN),
                PARAM(CONSOLE_EVTCHN),
        };
#undef PARAM

        if (op >= ARRAY_SIZE(names))
                return "unknown";

        if (!names[op])
                return "reserved";

        return names[op];
}

/**
 * hvm_get_parameter_maintain_dcache - function to obtain a HVM
 * parameter value.
 * @idx: HVM parameter index
 * @value: Value to fill in
 *
 * According to Xen on ARM ABI (xen/include/public/arch-arm.h):
 * all memory which is shared with other entities in the system
 * (including the hypervisor and other guests) must reside in memory
 * which is mapped as Normal Inner Write-Back Outer Write-Back
 * Inner-Shareable.
 *
 * Thus, page attributes must be equally set for all the entities
 * working with that page.
 *
 * Before MMU setup the data cache is turned off, so it means that
 * manual data cache maintenance is required, because of the
 * difference of page attributes.
 */
int hvm_get_parameter_maintain_dcache(int idx, uint64_t *value)
{
        struct xen_hvm_param xhv;
        int ret;

        invalidate_dcache_range((unsigned long)&xhv,
                                (unsigned long)&xhv + sizeof(xhv));
        xhv.domid = DOMID_SELF;
        xhv.index = idx;
        invalidate_dcache_range((unsigned long)&xhv,
                                (unsigned long)&xhv + sizeof(xhv));

        ret = HYPERVISOR_hvm_op(HVMOP_get_param, &xhv);
        if (ret < 0) {
                pr_err("Cannot get hvm parameter %s (%d): %d!\n",
                           param_name(idx), idx, ret);
                BUG();
        }
        invalidate_dcache_range((unsigned long)&xhv,
                                (unsigned long)&xhv + sizeof(xhv));

        *value = xhv.value;

        return ret;
}

int hvm_get_parameter(int idx, uint64_t *value)
{
        struct xen_hvm_param xhv;
        int ret;

        xhv.domid = DOMID_SELF;
        xhv.index = idx;
        ret = HYPERVISOR_hvm_op(HVMOP_get_param, &xhv);
        if (ret < 0) {
                pr_err("Cannot get hvm parameter %s (%d): %d!\n",
                           param_name(idx), idx, ret);
                BUG();
        }

        *value = xhv.value;

        return ret;
}

struct shared_info *map_shared_info(void *p)
{
        struct xen_add_to_physmap xatp;

        HYPERVISOR_shared_info = (struct shared_info *)memalign(PAGE_SIZE,
                                                                PAGE_SIZE);
        if (!HYPERVISOR_shared_info)
                BUG();

        xatp.domid = DOMID_SELF;
        xatp.idx = 0;
        xatp.space = XENMAPSPACE_shared_info;
        xatp.gpfn = virt_to_pfn(HYPERVISOR_shared_info);
        if (HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp) != 0)
                BUG();

        return HYPERVISOR_shared_info;
}

void unmap_shared_info(void)
{
        xen_pfn_t shared_info_pfn = virt_to_pfn(HYPERVISOR_shared_info);
        struct xen_remove_from_physmap xrfp = {0};
        struct xen_memory_reservation reservation = {0};
        xen_ulong_t nr_exts = 1;

        xrfp.domid = DOMID_SELF;
        xrfp.gpfn = shared_info_pfn;
        if (HYPERVISOR_memory_op(XENMEM_remove_from_physmap, &xrfp) != 0)
                panic("Failed to unmap HYPERVISOR_shared_info\n");

        /*
         * After removing from physmap there will be a hole in address space on
         * HYPERVISOR_shared_info address, so to free memory allocated with
         * memalign and prevent exceptions during access to this page we need to
         * fill this 4KB hole with XENMEM_populate_physmap before jumping to Linux.
         */
        reservation.domid = DOMID_SELF;
        reservation.extent_order = 0;
        reservation.address_bits = 0;
        set_xen_guest_handle(reservation.extent_start, &shared_info_pfn);
        reservation.nr_extents = nr_exts;
        if (HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation) != nr_exts)
                panic("Failed to populate memory on HYPERVISOR_shared_info addr\n");

        /* Now we can return this to memory allocator */
        free(HYPERVISOR_shared_info);
}

void do_hypervisor_callback(struct pt_regs *regs)
{
        unsigned long l1, l2, l1i, l2i;
        unsigned int port;
        int cpu = 0;
        struct shared_info *s = HYPERVISOR_shared_info;
        struct vcpu_info *vcpu_info = &s->vcpu_info[cpu];

        in_callback = 1;

        vcpu_info->evtchn_upcall_pending = 0;
        l1 = xchg(&vcpu_info->evtchn_pending_sel, 0);

        while (l1 != 0) {
                l1i = __ffs(l1);
                l1 &= ~(1UL << l1i);

                while ((l2 = active_evtchns(cpu, s, l1i)) != 0) {
                        l2i = __ffs(l2);
                        l2 &= ~(1UL << l2i);

                        port = (l1i * (sizeof(unsigned long) * 8)) + l2i;
                        do_event(port, regs);
                }
        }

        in_callback = 0;
}

void force_evtchn_callback(void)
{
#ifdef XEN_HAVE_PV_UPCALL_MASK
        int save;
#endif
        struct vcpu_info *vcpu;

        vcpu = &HYPERVISOR_shared_info->vcpu_info[smp_processor_id()];
#ifdef XEN_HAVE_PV_UPCALL_MASK
        save = vcpu->evtchn_upcall_mask;
#endif

        while (vcpu->evtchn_upcall_pending) {
#ifdef XEN_HAVE_PV_UPCALL_MASK
                vcpu->evtchn_upcall_mask = 1;
#endif
                do_hypervisor_callback(NULL);
#ifdef XEN_HAVE_PV_UPCALL_MASK
                vcpu->evtchn_upcall_mask = save;
#endif
        };
}

void mask_evtchn(uint32_t port)
{
        struct shared_info *s = HYPERVISOR_shared_info;

        synch_set_bit(port, &s->evtchn_mask[0]);
}

void unmask_evtchn(uint32_t port)
{
        struct shared_info *s = HYPERVISOR_shared_info;
        struct vcpu_info *vcpu_info = &s->vcpu_info[smp_processor_id()];

        synch_clear_bit(port, &s->evtchn_mask[0]);

        /*
         * Just like a real IO-APIC we 'lose the interrupt edge' if the
         * channel is masked.
         */
        if (synch_test_bit(port, &s->evtchn_pending[0]) &&
            !synch_test_and_set_bit(port / (sizeof(unsigned long) * 8),
                                    &vcpu_info->evtchn_pending_sel)) {
                vcpu_info->evtchn_upcall_pending = 1;
#ifdef XEN_HAVE_PV_UPCALL_MASK
                if (!vcpu_info->evtchn_upcall_mask)
#endif
                        force_evtchn_callback();
        }
}

void clear_evtchn(uint32_t port)
{
        struct shared_info *s = HYPERVISOR_shared_info;

        synch_clear_bit(port, &s->evtchn_pending[0]);
}

int xen_init(void)
{
        debug("%s\n", __func__);

        map_shared_info(NULL);
        init_events();
        init_xenbus();
        init_gnttab();

        return 0;
}

void xen_fini(void)
{
        debug("%s\n", __func__);

        fini_gnttab();
        fini_xenbus();
        fini_events();
        unmap_shared_info();
}