Re: [PATCH 0/3] AMD invpcid exception fix

[Bandan Das <bsd@redhat.com>]

Paolo Bonzini <pbonzini@redhat.com> writes:

> On 11/02/21 22:22, Bandan Das wrote:
>> The pcid-disabled test from kvm-unit-tests fails on a Milan host because the
>> processor injects a #GP while the test expects #UD. While setting the intercept
>> when the guest has it disabled seemed like the obvious thing to do, Babu Moger (AMD)
>> pointed me to an earlier discussion here - https://lkml.org/lkml/2020/6/11/949
>>
>> Jim points out there that  #GP has precedence over the intercept bit when invpcid is
>> called with CPL > 0 and so even if we intercept invpcid, the guest would end up with getting
>> and "incorrect" exception. To inject the right exception, I created an entry for the instruction
>> in the emulator to decode it successfully and then inject a UD instead of a GP when
>> the guest has it disabled.
>>
>> Bandan Das (3):
>>    KVM: Add a stub for invpcid in the emulator table
>>    KVM: SVM: Handle invpcid during gp interception
>>    KVM: SVM:  check if we need to track GP intercept for invpcid
>>
>>   arch/x86/kvm/emulate.c |  3 ++-
>>   arch/x86/kvm/svm/svm.c | 22 +++++++++++++++++++++-
>>   2 files changed, 23 insertions(+), 2 deletions(-)
>>
>
> Isn't this the same thing that "[PATCH 1/3] KVM: SVM: Intercept
> INVPCID when it's disabled to inject #UD" also does?
>
Yeah, Babu pointed me to Sean's series after I posted mine.
1/3 indeed will fix the kvm-unit-test failure. IIUC, It doesn't look like it
handles the case for the guest executing invpcid at CPL > 0 when it's
disabled for the guest - #GP takes precedence over intercepts and will
be incorrectly injected instead of an #UD.

Bandan
> Paolo