1 files changed, 135 insertions, 0 deletions
diff --git a/tools/testing/selftests/kvm/x86/kvm_buslock_test.c b/tools/testing/selftests/kvm/x86/kvm_buslock_test.c
new file mode 100644
index 000000000000..d88500c118eb
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86/kvm_buslock_test.c
@@ -0,0 +1,135 @@
+// 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;
+}