// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2020, Google LLC.
 *
 * Tests for KVM paravirtual feature disablement
 */
#include <asm/kvm_para.h>
#include <linux/kvm_para.h>
#include <linux/stringify.h>
#include <stdint.h>

#include "kvm_test_harness.h"
#include "apic.h"
#include "test_util.h"
#include "kvm_util.h"
#include "processor.h"

/* VMCALL and VMMCALL are both 3-byte opcodes. */
#define HYPERCALL_INSN_SIZE     3

static bool quirk_disabled;

static void guest_ud_handler(struct ex_regs *regs)
{
        regs->rax = -EFAULT;
        regs->rip += HYPERCALL_INSN_SIZE;
}

static const uint8_t vmx_vmcall[HYPERCALL_INSN_SIZE]  = { 0x0f, 0x01, 0xc1 };
static const uint8_t svm_vmmcall[HYPERCALL_INSN_SIZE] = { 0x0f, 0x01, 0xd9 };

extern uint8_t hypercall_insn[HYPERCALL_INSN_SIZE];
static uint64_t do_sched_yield(uint8_t apic_id)
{
        uint64_t ret;

        asm volatile("hypercall_insn:\n\t"
                     ".byte 0xcc,0xcc,0xcc\n\t"
                     : "=a"(ret)
                     : "a"((uint64_t)KVM_HC_SCHED_YIELD), "b"((uint64_t)apic_id)
                     : "memory");

        return ret;
}

static void guest_main(void)
{
        const uint8_t *native_hypercall_insn;
        const uint8_t *other_hypercall_insn;
        uint64_t ret;

        if (host_cpu_is_intel) {
                native_hypercall_insn = vmx_vmcall;
                other_hypercall_insn  = svm_vmmcall;
        } else if (host_cpu_is_amd) {
                native_hypercall_insn = svm_vmmcall;
                other_hypercall_insn  = vmx_vmcall;
        } else {
                GUEST_ASSERT(0);
                /* unreachable */
                return;
        }

        memcpy(hypercall_insn, other_hypercall_insn, HYPERCALL_INSN_SIZE);

        ret = do_sched_yield(GET_APIC_ID_FIELD(xapic_read_reg(APIC_ID)));

        /*
         * If the quirk is disabled, verify that guest_ud_handler() "returned"
         * -EFAULT and that KVM did NOT patch the hypercall.  If the quirk is
         * enabled, verify that the hypercall succeeded and that KVM patched in
         * the "right" hypercall.
         */
        if (quirk_disabled) {
                GUEST_ASSERT(ret == (uint64_t)-EFAULT);
                GUEST_ASSERT(!memcmp(other_hypercall_insn, hypercall_insn,
                             HYPERCALL_INSN_SIZE));
        } else {
                GUEST_ASSERT(!ret);
                GUEST_ASSERT(!memcmp(native_hypercall_insn, hypercall_insn,
                             HYPERCALL_INSN_SIZE));
        }

        GUEST_DONE();
}

KVM_ONE_VCPU_TEST_SUITE(fix_hypercall);

static void enter_guest(struct kvm_vcpu *vcpu)
{
        struct kvm_run *run = vcpu->run;
        struct ucall uc;

        vcpu_run(vcpu);
        switch (get_ucall(vcpu, &uc)) {
        case UCALL_SYNC:
                pr_info("%s: %016lx\n", (const char *)uc.args[2], uc.args[3]);
                break;
        case UCALL_DONE:
                return;
        case UCALL_ABORT:
                REPORT_GUEST_ASSERT(uc);
        default:
                TEST_FAIL("Unhandled ucall: %ld\nexit_reason: %u (%s)",
                          uc.cmd, run->exit_reason, exit_reason_str(run->exit_reason));
        }
}

static void test_fix_hypercall(struct kvm_vcpu *vcpu, bool disable_quirk)
{
        struct kvm_vm *vm = vcpu->vm;

        vm_install_exception_handler(vcpu->vm, UD_VECTOR, guest_ud_handler);

        if (disable_quirk)
                vm_enable_cap(vm, KVM_CAP_DISABLE_QUIRKS2,
                              KVM_X86_QUIRK_FIX_HYPERCALL_INSN);

        quirk_disabled = disable_quirk;
        sync_global_to_guest(vm, quirk_disabled);

        virt_pg_map(vm, APIC_DEFAULT_GPA, APIC_DEFAULT_GPA);

        enter_guest(vcpu);
}

KVM_ONE_VCPU_TEST(fix_hypercall, enable_quirk, guest_main)
{
        test_fix_hypercall(vcpu, false);
}

KVM_ONE_VCPU_TEST(fix_hypercall, disable_quirk, guest_main)
{
        test_fix_hypercall(vcpu, true);
}

int main(int argc, char *argv[])
{
        TEST_REQUIRE(kvm_check_cap(KVM_CAP_DISABLE_QUIRKS2) & KVM_X86_QUIRK_FIX_HYPERCALL_INSN);

        return test_harness_run(argc, argv);
}