// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2024 Advanced Micro Devices, Inc.
 */
#include <linux/atomic.h>

#include "kvm_util.h"
#include "processor.h"
#include "svm_util.h"
#include "vmx.h"
#include "test_util.h"

#define NR_BUS_LOCKS_PER_LEVEL 100
#define CACHE_LINE_SIZE         64

/*
 * To generate a bus lock, carve out a buffer that precisely occupies two cache
 * lines and perform an atomic access that splits the two lines.
 */
static u8 buffer[CACHE_LINE_SIZE * 2] __aligned(CACHE_LINE_SIZE);
static atomic_t *val = (void *)&buffer[CACHE_LINE_SIZE - (sizeof(*val) / 2)];

static void guest_generate_buslocks(void)
{
        for (int i = 0; i < NR_BUS_LOCKS_PER_LEVEL; i++)
                atomic_inc(val);
}

#define L2_GUEST_STACK_SIZE     64

static void l2_guest_code(void)
{
        guest_generate_buslocks();
        GUEST_DONE();
}

static void l1_svm_code(struct svm_test_data *svm)
{
        unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];
        struct vmcb *vmcb = svm->vmcb;

        generic_svm_setup(svm, l2_guest_code, &l2_guest_stack[L2_GUEST_STACK_SIZE]);
        run_guest(vmcb, svm->vmcb_gpa);
}

static void l1_vmx_code(struct vmx_pages *vmx)
{
        unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];

        GUEST_ASSERT_EQ(prepare_for_vmx_operation(vmx), true);
        GUEST_ASSERT_EQ(load_vmcs(vmx), true);

        prepare_vmcs(vmx, NULL, &l2_guest_stack[L2_GUEST_STACK_SIZE]);

        GUEST_ASSERT(!vmwrite(GUEST_RIP, (u64)l2_guest_code));
        GUEST_ASSERT(!vmlaunch());
}

static void guest_code(void *test_data)
{
        guest_generate_buslocks();

        if (this_cpu_has(X86_FEATURE_SVM))
                l1_svm_code(test_data);
        else if (this_cpu_has(X86_FEATURE_VMX))
                l1_vmx_code(test_data);
        else
                GUEST_DONE();

        TEST_FAIL("L2 should have signaled 'done'");
}

int main(int argc, char *argv[])
{
        const bool has_nested = kvm_cpu_has(X86_FEATURE_SVM) || kvm_cpu_has(X86_FEATURE_VMX);
        vm_vaddr_t nested_test_data_gva;
        struct kvm_vcpu *vcpu;
        struct kvm_run *run;
        struct kvm_vm *vm;
        int i, bus_locks = 0;

        TEST_REQUIRE(kvm_has_cap(KVM_CAP_X86_BUS_LOCK_EXIT));

        vm = vm_create(1);
        vm_enable_cap(vm, KVM_CAP_X86_BUS_LOCK_EXIT, KVM_BUS_LOCK_DETECTION_EXIT);
        vcpu = vm_vcpu_add(vm, 0, guest_code);

        if (kvm_cpu_has(X86_FEATURE_SVM))
                vcpu_alloc_svm(vm, &nested_test_data_gva);
        else
                vcpu_alloc_vmx(vm, &nested_test_data_gva);

        vcpu_args_set(vcpu, 1, nested_test_data_gva);

        run = vcpu->run;

        for (i = 0; i <= NR_BUS_LOCKS_PER_LEVEL * (1 + has_nested); i++) {
                struct ucall uc;

                vcpu_run(vcpu);

                if (run->exit_reason == KVM_EXIT_IO) {
                        switch (get_ucall(vcpu, &uc)) {
                        case UCALL_ABORT:
                                REPORT_GUEST_ASSERT(uc);
                                goto done;
                        case UCALL_SYNC:
                                continue;
                        case UCALL_DONE:
                                goto done;
                        default:
                                TEST_FAIL("Unknown ucall 0x%lx.", uc.cmd);
                        }
                }

                TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_X86_BUS_LOCK);

                /*
                 * Verify the counter is actually getting incremented, e.g. that
                 * KVM isn't skipping the instruction.  On Intel, the exit is
                 * trap-like, i.e. the counter should already have been
                 * incremented.  On AMD, it's fault-like, i.e. the counter will
                 * be incremented when the guest re-executes the instruction.
                 */
                sync_global_from_guest(vm, *val);
                TEST_ASSERT_EQ(atomic_read(val), bus_locks + host_cpu_is_intel);

                bus_locks++;
        }
        TEST_FAIL("Didn't receive UCALL_DONE, took %u bus lock exits\n", bus_locks);
done:
        TEST_ASSERT_EQ(i, bus_locks);
        kvm_vm_free(vm);
        return 0;
}