In x86's debug_regs test, change the RDMSR(MISC_ENABLES) in the single-step
testcase to a WRMSR(TSC_DEADLINE) in order to verify that KVM honors
KVM_GUESTDBG_SINGLESTEP when handling a fastpath VM-Exit.
Note, the extra coverage is effectively Intel-only, as KVM only handles
TSC_DEADLINE in the fastpath when the timer is emulated via the hypervisor
timer, a.k.a. the VMX preemption timer.
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
tools/testing/selftests/kvm/x86_64/debug_regs.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/tools/testing/selftests/kvm/x86_64/debug_regs.c b/tools/testing/selftests/kvm/x86_64/debug_regs.c
index f6b295e0b2d2..76cc2df9238a 100644
--- a/tools/testing/selftests/kvm/x86_64/debug_regs.c
+++ b/tools/testing/selftests/kvm/x86_64/debug_regs.c
@@ -47,15 +47,18 @@ static void guest_code(void)
/*
* Single step test, covers 2 basic instructions and 2 emulated
*
- * Enable interrupts during the single stepping to see that
- * pending interrupt we raised is not handled due to KVM_GUESTDBG_BLOCKIRQ
+ * Enable interrupts during the single stepping to see that pending
+ * interrupt we raised is not handled due to KVM_GUESTDBG_BLOCKIRQ.
+ *
+ * Write MSR_IA32_TSC_DEADLINE to verify that KVM's fastpath handler
+ * exits to userspace due to single-step being enabled.
*/
asm volatile("ss_start: "
"sti\n\t"
"xor %%eax,%%eax\n\t"
"cpuid\n\t"
- "movl $0x1a0,%%ecx\n\t"
- "rdmsr\n\t"
+ "movl $" __stringify(MSR_IA32_TSC_DEADLINE) ", %%ecx\n\t"
+ "wrmsr\n\t"
"cli\n\t"
: : : "eax", "ebx", "ecx", "edx");
base-commit: 332d2c1d713e232e163386c35a3ba0c1b90df83f
--
2.46.0.469.g59c65b2a67-goog
