[kvm-unit-tests,v2,2/2] x86: svm: Add SPEC_CTRL feature test

Commit Message

Babu Moger Jan. 29, 2021, 12:36 a.m. UTC

Add the SPEC_CTRL tests for SVM and make sure the settings on L2
guests does not overwrite the L1 guest's SPEC_CTRL settings.

Test Method.
1. Save the L1 guests SPEC_CTRL settings(rdmsr). Normally 0.
2. Start the L2 guest
3. Change the L2 guests SPEC_CTRL settings.
4. Exit the L2 guest.
5. Verify if the settings from step #1 still holds.

Signed-off-by: Babu Moger <[e-mail]>
---
 x86/svm_tests.c |   52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

Patch

diff --git a/x86/svm_tests.c b/x86/svm_tests.c
index 29a0b59..2867337 100644
--- a/x86/svm_tests.c
+++ b/x86/svm_tests.c
@@ -2002,6 +2002,55 @@  static bool init_intercept_check(struct svm_test *test)
     return init_intercept;
 }
 
+/* Indirect Branch Restricted Speculation(bit 0) */
+#define SPEC_CTRL_IBRS        1
+/* Single Thread Indirect Branch Predictor (STIBP)(bit 1) */
+#define SPEC_CTRL_STIBP       2
+/* Speculative Store Bypass Disable (bit 2) */
+#define SPEC_CTRL_SSBD        4
+
+static bool spec_ctrl_supported(void)
+{
+    return this_cpu_has(X86_FEATURE_AMD_SSBD) ||
+           this_cpu_has(X86_FEATURE_AMD_STIBP) ||
+           this_cpu_has(X86_FEATURE_AMD_IBRS);
+}
+
+static void spec_ctrl_prepare(struct svm_test *test)
+{
+    vmcb_ident(vmcb);
+    test->scratch = rdmsr(MSR_IA32_SPEC_CTRL);
+}
+
+/*
+ * Write it twice to bypass the interception. The first write to
+ * SPEC_CTRL is intercepted in older kernels.
+ */
+static void spec_ctrl_test(struct svm_test *test)
+{
+    int spec_ctrl = 0;
+
+    if (this_cpu_has(X86_FEATURE_AMD_SSBD))
+        spec_ctrl |= SPEC_CTRL_SSBD;
+    if (this_cpu_has(X86_FEATURE_AMD_STIBP))
+        spec_ctrl |= SPEC_CTRL_STIBP;
+    if (this_cpu_has(X86_FEATURE_AMD_IBRS))
+        spec_ctrl |= SPEC_CTRL_IBRS;
+
+    wrmsr(MSR_IA32_SPEC_CTRL, spec_ctrl);
+    wrmsr(MSR_IA32_SPEC_CTRL, spec_ctrl);
+}
+
+static bool spec_ctrl_finished(struct svm_test *test)
+{
+    return vmcb->control.exit_code == SVM_EXIT_VMMCALL;
+}
+
+static bool spec_ctrl_check(struct svm_test *test)
+{
+    return test->scratch == rdmsr(MSR_IA32_SPEC_CTRL);
+}
+
 #define TEST(name) { #name, .v2 = name }
 
 /*
@@ -2492,6 +2541,9 @@  struct svm_test svm_tests[] = {
     { "svm_init_intercept_test", smp_supported, init_intercept_prepare,
       default_prepare_gif_clear, init_intercept_test,
       init_intercept_finished, init_intercept_check, .on_vcpu = 2 },
+    { "SPEC_CTRL", spec_ctrl_supported, spec_ctrl_prepare,
+      default_prepare_gif_clear, spec_ctrl_test,
+      spec_ctrl_finished, spec_ctrl_check },
     TEST(svm_cr4_osxsave_test),
     TEST(svm_guest_state_test),
     TEST(svm_vmrun_errata_test),