* [PATCH] KVM: selftests: Don't skip L2's VMCALL in SMM test for SVM guest
@ 2022-01-25 22:17 Sean Christopherson
2022-01-26 15:23 ` Vitaly Kuznetsov
2022-01-26 15:45 ` Paolo Bonzini
0 siblings, 2 replies; 3+ messages in thread
From: Sean Christopherson @ 2022-01-25 22:17 UTC (permalink / raw)
To: Paolo Bonzini
Cc: Sean Christopherson, Vitaly Kuznetsov, Wanpeng Li, Jim Mattson,
Joerg Roedel, kvm, linux-kernel, Maxim Levitsky
Don't skip the vmcall() in l2_guest_code() prior to re-entering L2, doing
so will result in L2 running to completion, popping '0' off the stack for
RET, jumping to address '0', and ultimately dying with a triple fault
shutdown.
It's not at all obvious why the test re-enters L2 and re-executes VMCALL,
but presumably it serves a purpose. The VMX path doesn't skip vmcall(),
and the test can't possibly have passed on SVM, so just do what VMX does.
Fixes: d951b2210c1a ("KVM: selftests: smm_test: Test SMM enter from L2")
Cc: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
tools/testing/selftests/kvm/x86_64/smm_test.c | 1 -
1 file changed, 1 deletion(-)
diff --git a/tools/testing/selftests/kvm/x86_64/smm_test.c b/tools/testing/selftests/kvm/x86_64/smm_test.c
index 2da8eb8e2d96..a626d40fdb48 100644
--- a/tools/testing/selftests/kvm/x86_64/smm_test.c
+++ b/tools/testing/selftests/kvm/x86_64/smm_test.c
@@ -105,7 +105,6 @@ static void guest_code(void *arg)
if (cpu_has_svm()) {
run_guest(svm->vmcb, svm->vmcb_gpa);
- svm->vmcb->save.rip += 3;
run_guest(svm->vmcb, svm->vmcb_gpa);
} else {
vmlaunch();
base-commit: e2e83a73d7ce66f62c7830a85619542ef59c90e4
--
2.35.0.rc0.227.g00780c9af4-goog
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] KVM: selftests: Don't skip L2's VMCALL in SMM test for SVM guest
2022-01-25 22:17 [PATCH] KVM: selftests: Don't skip L2's VMCALL in SMM test for SVM guest Sean Christopherson
@ 2022-01-26 15:23 ` Vitaly Kuznetsov
2022-01-26 15:45 ` Paolo Bonzini
1 sibling, 0 replies; 3+ messages in thread
From: Vitaly Kuznetsov @ 2022-01-26 15:23 UTC (permalink / raw)
To: Sean Christopherson
Cc: Paolo Bonzini, Wanpeng Li, Jim Mattson, Joerg Roedel, kvm,
linux-kernel, Maxim Levitsky
Sean Christopherson <seanjc@google.com> writes:
> Don't skip the vmcall() in l2_guest_code() prior to re-entering L2, doing
> so will result in L2 running to completion, popping '0' off the stack for
> RET, jumping to address '0', and ultimately dying with a triple fault
> shutdown.
>
> It's not at all obvious why the test re-enters L2 and re-executes VMCALL,
> but presumably it serves a purpose.
I managed to forget everything but it seems my intentions were to test
two things:
- "Enter SMM during L2 execution and check that we correctly return from
it."
- "Perform save/restore while the guest is in SMM triggered during L2
execution"
the later could've been complemented with "and try running L2 after".
> The VMX path doesn't skip vmcall(), and the test can't possibly have
> passed on SVM
Well, it kind of works for me (pre-patch) :-) I do see #DF in the trace
but not #TF.
>, so just do what VMX does.
>
Makes sense. I can't recall how "+= 3" appeared.
> Fixes: d951b2210c1a ("KVM: selftests: smm_test: Test SMM enter from L2")
> Cc: Maxim Levitsky <mlevitsk@redhat.com>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> tools/testing/selftests/kvm/x86_64/smm_test.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/tools/testing/selftests/kvm/x86_64/smm_test.c b/tools/testing/selftests/kvm/x86_64/smm_test.c
> index 2da8eb8e2d96..a626d40fdb48 100644
> --- a/tools/testing/selftests/kvm/x86_64/smm_test.c
> +++ b/tools/testing/selftests/kvm/x86_64/smm_test.c
> @@ -105,7 +105,6 @@ static void guest_code(void *arg)
>
> if (cpu_has_svm()) {
> run_guest(svm->vmcb, svm->vmcb_gpa);
> - svm->vmcb->save.rip += 3;
> run_guest(svm->vmcb, svm->vmcb_gpa);
> } else {
> vmlaunch();
>
> base-commit: e2e83a73d7ce66f62c7830a85619542ef59c90e4
Reviewed-and-tested-by: Vitaly Kuznetsov <vkuznets@redhat.com>
--
Vitaly
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] KVM: selftests: Don't skip L2's VMCALL in SMM test for SVM guest
2022-01-25 22:17 [PATCH] KVM: selftests: Don't skip L2's VMCALL in SMM test for SVM guest Sean Christopherson
2022-01-26 15:23 ` Vitaly Kuznetsov
@ 2022-01-26 15:45 ` Paolo Bonzini
1 sibling, 0 replies; 3+ messages in thread
From: Paolo Bonzini @ 2022-01-26 15:45 UTC (permalink / raw)
To: Sean Christopherson
Cc: Vitaly Kuznetsov, Wanpeng Li, Jim Mattson, Joerg Roedel, kvm,
linux-kernel, Maxim Levitsky
On 1/25/22 23:17, Sean Christopherson wrote:
> Don't skip the vmcall() in l2_guest_code() prior to re-entering L2, doing
> so will result in L2 running to completion, popping '0' off the stack for
> RET, jumping to address '0', and ultimately dying with a triple fault
> shutdown.
>
> It's not at all obvious why the test re-enters L2 and re-executes VMCALL,
> but presumably it serves a purpose. The VMX path doesn't skip vmcall(),
> and the test can't possibly have passed on SVM, so just do what VMX does.
>
> Fixes: d951b2210c1a ("KVM: selftests: smm_test: Test SMM enter from L2")
> Cc: Maxim Levitsky <mlevitsk@redhat.com>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> tools/testing/selftests/kvm/x86_64/smm_test.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/tools/testing/selftests/kvm/x86_64/smm_test.c b/tools/testing/selftests/kvm/x86_64/smm_test.c
> index 2da8eb8e2d96..a626d40fdb48 100644
> --- a/tools/testing/selftests/kvm/x86_64/smm_test.c
> +++ b/tools/testing/selftests/kvm/x86_64/smm_test.c
> @@ -105,7 +105,6 @@ static void guest_code(void *arg)
>
> if (cpu_has_svm()) {
> run_guest(svm->vmcb, svm->vmcb_gpa);
> - svm->vmcb->save.rip += 3;
> run_guest(svm->vmcb, svm->vmcb_gpa);
> } else {
> vmlaunch();
>
> base-commit: e2e83a73d7ce66f62c7830a85619542ef59c90e4
Queued, thanks.
Paolo
^ permalink raw reply [flat|nested] 3+ messages in thread
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2022-01-25 22:17 [PATCH] KVM: selftests: Don't skip L2's VMCALL in SMM test for SVM guest Sean Christopherson
2022-01-26 15:23 ` Vitaly Kuznetsov
2022-01-26 15:45 ` Paolo Bonzini
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