[PATCH v3 4/4] KVM: selftests: Add bus lock exit test

[Manali Shukla <manali.shukla@amd.com>]

From: Nikunj A Dadhania <nikunj@amd.com>

Add a test case to verify the Bus Lock exit feature

The main thing that the selftest verifies is that when a Buslock is
generated in the guest context, the KVM_EXIT_X86_BUS_LOCK is triggered
for SVM or VMX when the KVM capability KVM_CAP_X86_BUS_LOCK_EXIT is
enabled.

This test case also verifies the Bus Lock exit in nested scenario.

Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Co-developed-by: Manali Shukla <manali.shukla@amd.com>
Signed-off-by: Manali Shukla <manali.shukla@amd.com>
---
 tools/testing/selftests/kvm/Makefile          |   1 +
 .../selftests/kvm/x86_64/kvm_buslock_test.c   | 130 ++++++++++++++++++
 2 files changed, 131 insertions(+)
 create mode 100644 tools/testing/selftests/kvm/x86_64/kvm_buslock_test.c

diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index 960cf6a77198..b2de61e4a213 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -81,6 +81,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/hyperv_svm_test
 TEST_GEN_PROGS_x86_64 += x86_64/hyperv_tlb_flush
 TEST_GEN_PROGS_x86_64 += x86_64/kvm_clock_test
 TEST_GEN_PROGS_x86_64 += x86_64/kvm_pv_test
+TEST_GEN_PROGS_x86_64 += x86_64/kvm_buslock_test
 TEST_GEN_PROGS_x86_64 += x86_64/monitor_mwait_test
 TEST_GEN_PROGS_x86_64 += x86_64/nested_exceptions_test
 TEST_GEN_PROGS_x86_64 += x86_64/platform_info_test
diff --git a/tools/testing/selftests/kvm/x86_64/kvm_buslock_test.c b/tools/testing/selftests/kvm/x86_64/kvm_buslock_test.c
new file mode 100644
index 000000000000..82693520485c
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86_64/kvm_buslock_test.c
@@ -0,0 +1,130 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2024 Advanced Micro Devices, Inc.
+ */
+
+#include "test_util.h"
+#include "kvm_util.h"
+#include "processor.h"
+#include "svm_util.h"
+#include "vmx.h"
+
+#define NR_ITERATIONS 100
+#define L2_GUEST_STACK_SIZE 64
+
+struct buslock_test {
+	unsigned char pad[PAGE_SIZE - 2];
+	atomic_long_t val;
+} __packed;
+
+struct buslock_test test __aligned(PAGE_SIZE);
+
+static __always_inline void buslock_atomic_add(int i, atomic_long_t *v)
+{
+	asm volatile(LOCK_PREFIX "addl %1,%0"
+		     : "+m" (v->counter)
+		     : "ir" (i) : "memory");
+}
+
+static void buslock_add(void)
+{
+	/*
+	 * Increment a page unaligned variable atomically.
+	 * This should generate a bus lock exit.
+	 */
+	for (int i = 0; i < NR_ITERATIONS; i++)
+		buslock_atomic_add(2, &test.val);
+}
+
+static void l2_guest_code(void)
+{
+	buslock_add();
+	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);
+	GUEST_ASSERT(vmcb->control.exit_code == SVM_EXIT_VMMCALL);
+	GUEST_DONE();
+}
+
+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());
+
+	GUEST_ASSERT_EQ(vmreadz(VM_EXIT_REASON), EXIT_REASON_VMCALL);
+	GUEST_DONE();
+}
+
+static void guest_code(void *test_data)
+{
+	buslock_add();
+
+	if (this_cpu_has(X86_FEATURE_SVM))
+		l1_svm_code(test_data);
+	else
+		l1_vmx_code(test_data);
+}
+
+int main(int argc, char *argv[])
+{
+	struct kvm_vcpu *vcpu;
+	struct kvm_run *run;
+	struct kvm_vm *vm;
+	vm_vaddr_t nested_test_data_gva;
+
+	TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_SVM) || kvm_cpu_has(X86_FEATURE_VMX));
+	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 (;;) {
+		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);
+				/* NOT REACHED */
+			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);
+	}
+done:
+	kvm_vm_free(vm);
+	return 0;
+}
-- 
2.34.1