According to section "VMRUN and TF/RF Bits in EFLAGS" in AMD APM vol 2,
"From the host point of view, VMRUN acts like a single instruction,
even though an arbitrary number of guest instructions may execute
before a #VMEXIT effectively completes the VMRUN. As a single
host instruction, VMRUN interacts with EFLAGS.TF like ordinary
instructions. EFLAGS.TF causes a #DB trap after the VMRUN completes
on the host side (i.e., after the #VMEXIT from the guest).
Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>
---
x86/svm_tests.c | 115 ++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 115 insertions(+)
diff --git a/x86/svm_tests.c b/x86/svm_tests.c
index 29a0b59..466a13c 100644
--- a/x86/svm_tests.c
+++ b/x86/svm_tests.c
@@ -2002,6 +2002,118 @@ static bool init_intercept_check(struct svm_test *test)
return init_intercept;
}
+/*
+ * Setting host EFLAGS.TF causes a #DB trap after the VMRUN completes on the
+ * host side (i.e., after the #VMEXIT from the guest).
+ *
+ * [AMD APM]
+ */
+static volatile u8 host_rflags_guest_main_flag = 0;
+static volatile u8 host_rflags_db_handler_flag = 0;
+static volatile bool host_rflags_ss_on_vmrun = false;
+static volatile bool host_rflags_vmrun_reached = false;
+static volatile bool host_rflags_set_tf = false;
+static u64 post_vmrun_rip;
+
+extern void *vmrun_rip;
+
+static void host_rflags_db_handler(struct ex_regs *r)
+{
+ if (host_rflags_ss_on_vmrun) {
+ if (host_rflags_vmrun_reached) {
+ r->rflags &= ~X86_EFLAGS_TF;
+ post_vmrun_rip = r->rip;
+ } else {
+ if (r->rip == (u64)(&vmrun_rip))
+ host_rflags_vmrun_reached = true;
+ }
+ } else {
+ r->rflags &= ~X86_EFLAGS_TF;
+ }
+}
+
+static void host_rflags_prepare(struct svm_test *test)
+{
+ default_prepare(test);
+ handle_exception(DB_VECTOR, host_rflags_db_handler);
+ set_test_stage(test, 0);
+}
+
+static void host_rflags_prepare_gif_clear(struct svm_test *test)
+{
+ if (host_rflags_set_tf)
+ write_rflags(read_rflags() | X86_EFLAGS_TF);
+}
+
+static void host_rflags_test(struct svm_test *test)
+{
+ while (1) {
+ if (get_test_stage(test) > 0 && host_rflags_set_tf &&
+ (!host_rflags_ss_on_vmrun) &&
+ (!host_rflags_db_handler_flag))
+ host_rflags_guest_main_flag = 1;
+ vmmcall();
+ if (get_test_stage(test) == 3)
+ break;
+ }
+}
+
+static bool host_rflags_finished(struct svm_test *test)
+{
+ switch (get_test_stage(test)) {
+ case 0:
+ if (vmcb->control.exit_code != SVM_EXIT_VMMCALL) {
+ report(false, "Unexpected VMEXIT. Exit reason 0x%x",
+ vmcb->control.exit_code);
+ return true;
+ }
+ vmcb->save.rip += 3;
+ /*
+ * Setting host EFLAGS.TF not immediately before VMRUN, causes
+ * #DB trap before first guest instruction is executed
+ */
+ host_rflags_set_tf = true;
+ break;
+ case 1:
+ if (vmcb->control.exit_code != SVM_EXIT_VMMCALL ||
+ (!host_rflags_guest_main_flag)) {
+ report(false, "Unexpected VMEXIT or #DB handler"
+ " invoked before guest main. Exit reason 0x%x",
+ vmcb->control.exit_code);
+ return true;
+ }
+ vmcb->save.rip += 3;
+ /*
+ * Setting host EFLAGS.TF immediately before VMRUN, causes #DB
+ * trap after VMRUN completes on the host side (i.e., after
+ * VMEXIT from guest).
+ */
+ host_rflags_ss_on_vmrun = true;
+ break;
+ case 2:
+ if (vmcb->control.exit_code != SVM_EXIT_VMMCALL ||
+ post_vmrun_rip - (u64)(&vmrun_rip) != 3) {
+ report(false, "Unexpected VMEXIT or RIP mismatch."
+ " Exit reason 0x%x, VMRUN RIP: %lx, post-VMRUN"
+ " RIP: %lx", vmcb->control.exit_code,
+ (u64)(&vmrun_rip), post_vmrun_rip);
+ return true;
+ }
+ host_rflags_set_tf = false;
+ vmcb->save.rip += 3;
+ break;
+ default:
+ return true;
+ }
+ inc_test_stage(test);
+ return get_test_stage(test) == 4;
+}
+
+static bool host_rflags_check(struct svm_test *test)
+{
+ return get_test_stage(test) == 3;
+}
+
#define TEST(name) { #name, .v2 = name }
/*
@@ -2492,6 +2604,9 @@ 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 },
+ { "host_rflags", default_supported, host_rflags_prepare,
+ host_rflags_prepare_gif_clear, host_rflags_test,
+ host_rflags_finished, host_rflags_check },
TEST(svm_cr4_osxsave_test),
TEST(svm_guest_state_test),
TEST(svm_vmrun_errata_test),
--
2.27.0
