Re: [PATCH 5/8] KVM: SVM: Re-inject INT3/INTO instead of retrying the instruction

Maciej S. Szmigiero
2022-04-04T21:37:33Z

>>> index 47e7427d0395..a770a1c7ddd2 100644
>>> --- a/arch/x86/kvm/svm/svm.h
>>> +++ b/arch/x86/kvm/svm/svm.h
>>> @@ -230,8 +230,8 @@ struct vcpu_svm {
>>> bool nmi_singlestep;
>>> u64 nmi_singlestep_guest_rflags;
>>>
>>> - unsigned int3_injected;
>>> - unsigned long int3_rip;
>>> + unsigned soft_int_injected;
>>> + unsigned long soft_int_linear_rip;
>>>
>>> /* optional nested SVM features that are enabled for this guest */
>>> bool nrips_enabled : 1;
>>
>>
>> I mostly agree with this patch, but think that it doesn't address the
>> original issue that Maciej wanted to address:
>>
>> Suppose that there is *no* instruction in L2 code which caused the software
>> exception, but rather L1 set arbitrary next_rip, and set EVENTINJ to software
>> exception with some vector, and that injection got interrupted.
>>
>> I don't think that this code will support this.
>
> Argh, you're right. Maciej's selftest injects without an instruction, but it doesn't
> configure the scenario where that injection fails due to an exception+VM-Exit that
> isn't intercepted by L1 and is handled by L0. The event_inj test gets the coverage
> for the latter, but always has a backing instruction.

Still reviewing the whole patch set, but want to clear this point quickly:
The selftest does have an implicit intervening NPF (handled by L0) while
injecting the first L1 -> L2 event.

Thanks,
Maciej