Re: [PATCH] x86/svm: Provide EXITINFO decodes for MOV CR/DR intercepts

[Jan Beulich <jbeulich@xxxxxxxx>]

On 06.04.2023 11:52, Andrew Cooper wrote:
> On 06/04/2023 10:31 am, Jan Beulich wrote:
>> On 05.04.2023 22:44, Andrew Cooper wrote:
>>> --- a/xen/arch/x86/include/asm/hvm/svm/vmcb.h
>>> +++ b/xen/arch/x86/include/asm/hvm/svm/vmcb.h
>>> @@ -450,6 +450,11 @@ struct vmcb_struct {
>>>  
>>>                  uint64_t nrip;
>>>              } io;
>>> +            struct {
>>> +                uint64_t gpr:4;
>>> +                uint64_t :59;
>>> +                bool     mov_insn:1; /* MOV, as opposed to LMSW, CLTS, etc 
>>> */
>>> +            } mov;
>> The field being named just "mov" makes it apparently applicable to DRn
>> moves, too (and the title supports this), yet the top bit doesn't have
>> this meaning there. So perhaps say "MOV-CR" (or alike) in the comment?
> 
> Hmm - I'd not spotted that distinction.
> 
> Xen never decodes the exitinfo for a DR access - we just resync dr
> state, drop the intercept and reenter the guest.
> 
> Therefore I think it would be better to rename "mov" to "mov_cr" so you
> can't use the mov_insn field in a context that plausibly looks like a dr
> access.
> 
> Thoughts?

That was my other thought; it merely seemed to me that updating the comment
would allow future (if ever) use with MOV-DR. So yes, if you prefer going
that route: Fine with me.

Jan