kvm_buslock_test.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Copyright (C) 2024 Advanced Micro Devices, Inc.
  4 */
  5#include <linux/atomic.h>
  6
  7#include "kvm_util.h"
  8#include "processor.h"
  9#include "svm_util.h"
 10#include "vmx.h"
 11#include "test_util.h"
 12
 13#define NR_BUS_LOCKS_PER_LEVEL 100
 14#define CACHE_LINE_SIZE		64
 15
 16/*
 17 * To generate a bus lock, carve out a buffer that precisely occupies two cache
 18 * lines and perform an atomic access that splits the two lines.
 19 */
 20static u8 buffer[CACHE_LINE_SIZE * 2] __aligned(CACHE_LINE_SIZE);
 21static atomic_t *val = (void *)&buffer[CACHE_LINE_SIZE - (sizeof(*val) / 2)];
 22
 23static void guest_generate_buslocks(void)
 24{
 25	for (int i = 0; i < NR_BUS_LOCKS_PER_LEVEL; i++)
 26		atomic_inc(val);
 27}
 28
 29#define L2_GUEST_STACK_SIZE	64
 30
 31static void l2_guest_code(void)
 32{
 33	guest_generate_buslocks();
 34	GUEST_DONE();
 35}
 36
 37static void l1_svm_code(struct svm_test_data *svm)
 38{
 39	unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];
 40	struct vmcb *vmcb = svm->vmcb;
 41
 42	generic_svm_setup(svm, l2_guest_code, &l2_guest_stack[L2_GUEST_STACK_SIZE]);
 43	run_guest(vmcb, svm->vmcb_gpa);
 44}
 45
 46static void l1_vmx_code(struct vmx_pages *vmx)
 47{
 48	unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];
 49
 50	GUEST_ASSERT_EQ(prepare_for_vmx_operation(vmx), true);
 51	GUEST_ASSERT_EQ(load_vmcs(vmx), true);
 52
 53	prepare_vmcs(vmx, NULL, &l2_guest_stack[L2_GUEST_STACK_SIZE]);
 54
 55	GUEST_ASSERT(!vmwrite(GUEST_RIP, (u64)l2_guest_code));
 56	GUEST_ASSERT(!vmlaunch());
 57}
 58
 59static void guest_code(void *test_data)
 60{
 61	guest_generate_buslocks();
 62
 63	if (this_cpu_has(X86_FEATURE_SVM))
 64		l1_svm_code(test_data);
 65	else if (this_cpu_has(X86_FEATURE_VMX))
 66		l1_vmx_code(test_data);
 67	else
 68		GUEST_DONE();
 69
 70	TEST_FAIL("L2 should have signaled 'done'");
 71}
 72
 73int main(int argc, char *argv[])
 74{
 75	const bool has_nested = kvm_cpu_has(X86_FEATURE_SVM) || kvm_cpu_has(X86_FEATURE_VMX);
 76	vm_vaddr_t nested_test_data_gva;
 77	struct kvm_vcpu *vcpu;
 78	struct kvm_run *run;
 79	struct kvm_vm *vm;
 80	int i, bus_locks = 0;
 81
 82	TEST_REQUIRE(kvm_has_cap(KVM_CAP_X86_BUS_LOCK_EXIT));
 83
 84	vm = vm_create(1);
 85	vm_enable_cap(vm, KVM_CAP_X86_BUS_LOCK_EXIT, KVM_BUS_LOCK_DETECTION_EXIT);
 86	vcpu = vm_vcpu_add(vm, 0, guest_code);
 87
 88	if (kvm_cpu_has(X86_FEATURE_SVM))
 89		vcpu_alloc_svm(vm, &nested_test_data_gva);
 90	else
 91		vcpu_alloc_vmx(vm, &nested_test_data_gva);
 92
 93	vcpu_args_set(vcpu, 1, nested_test_data_gva);
 94
 95	run = vcpu->run;
 96
 97	for (i = 0; i <= NR_BUS_LOCKS_PER_LEVEL * (1 + has_nested); i++) {
 98		struct ucall uc;
 99
100		vcpu_run(vcpu);
101
102		if (run->exit_reason == KVM_EXIT_IO) {
103			switch (get_ucall(vcpu, &uc)) {
104			case UCALL_ABORT:
105				REPORT_GUEST_ASSERT(uc);
106				goto done;
107			case UCALL_SYNC:
108				continue;
109			case UCALL_DONE:
110				goto done;
111			default:
112				TEST_FAIL("Unknown ucall 0x%lx.", uc.cmd);
113			}
114		}
115
116		TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_X86_BUS_LOCK);
117
118		/*
119		 * Verify the counter is actually getting incremented, e.g. that
120		 * KVM isn't skipping the instruction.  On Intel, the exit is
121		 * trap-like, i.e. the counter should already have been
122		 * incremented.  On AMD, it's fault-like, i.e. the counter will
123		 * be incremented when the guest re-executes the instruction.
124		 */
125		sync_global_from_guest(vm, *val);
126		TEST_ASSERT_EQ(atomic_read(val), bus_locks + host_cpu_is_intel);
127
128		bus_locks++;
129	}
130	TEST_FAIL("Didn't receive UCALL_DONE, took %u bus lock exits\n", bus_locks);
131done:
132	TEST_ASSERT_EQ(i, bus_locks);
133	kvm_vm_free(vm);
134	return 0;
135}