Re: [Xen-devel] [PATCH v1 2/2] hvm/svm: Enable EMUL_UNIMPLEMENTED events on svm

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

On 05/18/2018 07:00 PM, Tamas K Lengyel wrote:
> On Fri, May 18, 2018 at 9:32 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>>>>> On 11.05.18 at 13:11, <aisaila@xxxxxxxxxxxxxxx> wrote:
>>> Signed-off-by: Alexandru Isaila <aisaila@xxxxxxxxxxxxxxx>
>>
>> It would be helpful to know whether this patch depends on patch 1 in any way.
>> If it doesn't, with Tamas'es ack this could go in independent of the other 
>> one.
>> For conveying such information a cover letter is usually helpful.
> 
> The two types of events are independent, you can trigger emulation
> without mem_access restrictions, although that is the one mostly used.

Indeed, it usually only makes sense to emulate an instruction that has
caused a page fault vm_event (something that's accessing a restricted
page), but it is possible to set the emulate flag when replying to a CR
or MSR write event.

We've waited this long to send this patch out because at least our use
cases always only involve emulating as a response to page fault events
(for MSR and CR writes we are only interested in being able to deny the
write) - but functionally there's no reason why this patch needs to wait
for the mem_access one.


Thanks,
Razvan

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