From: Sean Christopherson Date: Fri, 30 Aug 2024 04:44:48 +0000 (-0700) Subject: KVM: selftests: Verify single-stepping a fastpath VM-Exit exits to userspace X-Git-Tag: v6.12-rc1~11^2~5^2 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=c32e028057f144f15c06e2f09dfec49b14311910;p=thirdparty%2Fkernel%2Flinux.git KVM: selftests: Verify single-stepping a fastpath VM-Exit exits to userspace 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. Link: https://lore.kernel.org/r/20240830044448.130449-1-seanjc@google.com Signed-off-by: Sean Christopherson --- diff --git a/tools/testing/selftests/kvm/x86_64/debug_regs.c b/tools/testing/selftests/kvm/x86_64/debug_regs.c index f6b295e0b2d2b..76cc2df9238a3 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");