[PATCH kvm-unit-tests] SVM: move guest past HLT

[PATCH kvm-unit-tests] SVM: move guest past HLT

[Paolo Bonzini]

On AMD, the guest is not woken up from HLT by the interrupt or NMI vmexits.
Therefore we have to fix up the RIP manually.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 x86/svm_tests.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/x86/svm_tests.c b/x86/svm_tests.c
index c2725af..1f2975c 100644
--- a/x86/svm_tests.c
+++ b/x86/svm_tests.c
@@ -1316,6 +1316,11 @@ static bool interrupt_finished(struct svm_test *test)
             return true;
         }
 
+        /* The guest is not woken up from HLT, unlike Intel.  Fix that up.  */
+        if (get_test_stage(test) == 3) {
+            vmcb->save.rip++;
+        }
+
         irq_enable();
         asm volatile ("nop");
         irq_disable();
@@ -1501,6 +1506,9 @@ static bool nmi_hlt_finished(struct svm_test *test)
             return true;
         }
 
+        /* The guest is not woken up from HLT, unlike Intel.  Fix that up.  */
+        vmcb->save.rip++;
+
         report(true, "NMI intercept while running guest");
         break;
 
-- 
2.18.2

Re: [PATCH kvm-unit-tests] SVM: move guest past HLT

[Sean Christopherson]

On Thu, Apr 23, 2020 at 01:06:53PM -0400, Paolo Bonzini wrote:
> On AMD, the guest is not woken up from HLT by the interrupt or NMI vmexits.
> Therefore we have to fix up the RIP manually.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  x86/svm_tests.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/x86/svm_tests.c b/x86/svm_tests.c
> index c2725af..1f2975c 100644
> --- a/x86/svm_tests.c
> +++ b/x86/svm_tests.c
> @@ -1316,6 +1316,11 @@ static bool interrupt_finished(struct svm_test *test)
>              return true;
>          }
>  
> +        /* The guest is not woken up from HLT, unlike Intel.  Fix that up.  */

The comment about "unlike Intel" isn't correct, or at least it's not always
correct.  Intercept NMIs/interrupts don't affect vmcs.GUEST_ACTIVITY, i.e.
if the guest was in HLT before the exit then that's what will be recorded
in the VMCS.

https://lkml.kernel.org/r/20190509204838.GC12810@linux.intel.com

> +        if (get_test_stage(test) == 3) {
> +            vmcb->save.rip++;
> +        }
> +
>          irq_enable();
>          asm volatile ("nop");
>          irq_disable();
> @@ -1501,6 +1506,9 @@ static bool nmi_hlt_finished(struct svm_test *test)
>              return true;
>          }
>  
> +        /* The guest is not woken up from HLT, unlike Intel.  Fix that up.  */
> +        vmcb->save.rip++;
> +
>          report(true, "NMI intercept while running guest");
>          break;
>  
> -- 
> 2.18.2
> 

Re: [PATCH kvm-unit-tests] SVM: move guest past HLT

[Paolo Bonzini]

On 23/04/20 21:46, Sean Christopherson wrote:
>>  
>> +        /* The guest is not woken up from HLT, unlike Intel.  Fix that up.  */
> The comment about "unlike Intel" isn't correct, or at least it's not always
> correct.  Intercept NMIs/interrupts don't affect vmcs.GUEST_ACTIVITY, i.e.
> if the guest was in HLT before the exit then that's what will be recorded
> in the VMCS.
> 
> https://lkml.kernel.org/r/20190509204838.GC12810@linux.intel.com

Ok, I'll change it to "The guest is not woken up from HLT and RIP still
points to it".

On Intel indeed it is not woken up either but vmx_tests.c has

                if (vmx_get_test_stage() >= 2)
                        vmcs_write(GUEST_ACTV_STATE, ACTV_ACTIVE);

Then it's not surprising that, when I fixed a bunch of nested AMD things
to behave the same as in vmx/vmx.c, SVM broke and needed this patch.

Paolo