[PATCH 04/12] KVM: selftests: Extend vmx_nested_tsc_scaling_test to cover SVM

Yosry Ahmed
2025-10-01T14:58:46Z

From: Yosry Ahmed <yosryahmed@google.com>

Add SVM L1 code to run the nested guest, and allow the test to run with
SVM as well as VMX.

Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
---
tools/testing/selftests/kvm/Makefile.kvm | 2 +-
...aling_test.c => nested_tsc_scaling_test.c} | 48 +++++++++++++++++--
2 files changed, 44 insertions(+), 6 deletions(-)
rename tools/testing/selftests/kvm/x86/{vmx_nested_tsc_scaling_test.c => nested_tsc_scaling_test.c} (83%)

diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
index 61c6abdc9b36f..dc68147ace97f 100644
--- a/tools/testing/selftests/kvm/Makefile.kvm
+++ b/tools/testing/selftests/kvm/Makefile.kvm
@@ -118,7 +118,7 @@ TEST_GEN_PROGS_x86 += x86/vmx_msrs_test
TEST_GEN_PROGS_x86 += x86/vmx_invalid_nested_guest_state
TEST_GEN_PROGS_x86 += x86/set_nested_state_test
TEST_GEN_PROGS_x86 += x86/vmx_tsc_adjust_test
-TEST_GEN_PROGS_x86 += x86/vmx_nested_tsc_scaling_test
+TEST_GEN_PROGS_x86 += x86/nested_tsc_scaling_test
TEST_GEN_PROGS_x86 += x86/apic_bus_clock_test
TEST_GEN_PROGS_x86 += x86/xapic_ipi_test
TEST_GEN_PROGS_x86 += x86/xapic_state_test
diff --git a/tools/testing/selftests/kvm/x86/vmx_nested_tsc_scaling_test.c b/tools/testing/selftests/kvm/x86/nested_tsc_scaling_test.c
similarity index 83%
rename from tools/testing/selftests/kvm/x86/vmx_nested_tsc_scaling_test.c
rename to tools/testing/selftests/kvm/x86/nested_tsc_scaling_test.c
index 1759fa5cb3f29..56ab91544775f 100644
--- a/tools/testing/selftests/kvm/x86/vmx_nested_tsc_scaling_test.c
+++ b/tools/testing/selftests/kvm/x86/nested_tsc_scaling_test.c
@@ -13,6 +13,7 @@

#include "kvm_util.h"
#include "vmx.h"
+#include "svm_util.h"
#include "kselftest.h"

/* L2 is scaled up (from L1's perspective) by this factor */
@@ -79,7 +80,30 @@ static void l2_guest_code(void)
__asm__ __volatile__("vmcall");
}

-static void l1_guest_code(struct vmx_pages *vmx_pages)
+static void l1_svm_code(struct svm_test_data *svm)
+{
+ unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];
+
+ /* check that L1's frequency looks alright before launching L2 */
+ check_tsc_freq(UCHECK_L1);
+
+ generic_svm_setup(svm, l2_guest_code,
+ &l2_guest_stack[L2_GUEST_STACK_SIZE]);
+
+ /* enable TSC scaling for L2 */
+ wrmsr(MSR_AMD64_TSC_RATIO, (L2_SCALE_FACTOR << 32) | 1);
+
+ /* launch L2 */
+ run_guest(svm->vmcb, svm->vmcb_gpa);
+ GUEST_ASSERT(svm->vmcb->control.exit_code == SVM_EXIT_VMMCALL);
+
+ /* check that L1's frequency still looks good */
+ check_tsc_freq(UCHECK_L1);
+
+ GUEST_DONE();
+}
+
+static void l1_vmx_code(struct vmx_pages *vmx_pages)
{
unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];
uint32_t control;
@@ -116,11 +140,19 @@ static void l1_guest_code(struct vmx_pages *vmx_pages)
GUEST_DONE();
}

+static void l1_guest_code(void *data)
+{
+ if (this_cpu_has(X86_FEATURE_VMX))
+ l1_vmx_code(data);
+ else
+ l1_svm_code(data);
+}
+
int main(int argc, char *argv[])
{
struct kvm_vcpu *vcpu;
struct kvm_vm *vm;
- vm_vaddr_t vmx_pages_gva;
+ vm_vaddr_t guest_gva = 0;

uint64_t tsc_start, tsc_end;
uint64_t tsc_khz;
@@ -129,7 +161,8 @@ int main(int argc, char *argv[])
uint64_t l1_tsc_freq = 0;
uint64_t l2_tsc_freq = 0;

- TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_VMX));
+ TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_VMX) ||
+ kvm_cpu_has(X86_FEATURE_SVM));
TEST_REQUIRE(kvm_has_cap(KVM_CAP_TSC_CONTROL));
TEST_REQUIRE(sys_clocksource_is_based_on_tsc());

@@ -152,8 +185,13 @@ int main(int argc, char *argv[])
printf("real TSC frequency is around: %"PRIu64"\n", l0_tsc_freq);

vm = vm_create_with_one_vcpu(&vcpu, l1_guest_code);
- vcpu_alloc_vmx(vm, &vmx_pages_gva);
- vcpu_args_set(vcpu, 1, vmx_pages_gva);
+
+ if (kvm_cpu_has(X86_FEATURE_VMX))
+ vcpu_alloc_vmx(vm, &guest_gva);
+ else
+ vcpu_alloc_svm(vm, &guest_gva);
+
+ vcpu_args_set(vcpu, 1, guest_gva);

tsc_khz = __vcpu_ioctl(vcpu, KVM_GET_TSC_KHZ, NULL);
TEST_ASSERT(tsc_khz != -1, "vcpu ioctl KVM_GET_TSC_KHZ failed");
--
2.51.0.618.g983fd99d29-goog