Re: [Xen-devel] [Patch RFC 00/13] VT-d Asynchronous Device-TLB Flush for ATS Device

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.09.15 at 16:03, <quan.xu@xxxxxxxxx> wrote:

>>>> On 21.09.15 at 20:04, < JBeulich@xxxxxxxx > wrote:
>> >>> On 21.09.15 at 11:46, <quan.xu@xxxxxxxxx> wrote:
>> >>> >>> On 21.09.15 at 16:51, < JBeulich@xxxxxxxx > wrote:
>> >>- Anything else?
>> >
>> >
>> > Just test the extreme case. The ATS specification mandates a timeout
>> > of 1 _minute_ for cache flush, even though it doesn't take so much
>> > time for cache flush.
>> > In my design, if the Device-TLB is not completed, the domain's vCPUs
>> > are not allowed entry guest mode (patch #7), otherwise, the logic is not
>> correct.
>> 
>> Hmm, that would be a serious limitation, and I can't immediately see a 
> reason:
>> Taking this with virtualization removed, I don't think such an invalidation 
> would
>> stall a physical CPU for a whole minute. Sadly I also can't immediately 
> think of a
>> solution, but I guess first of all I'll have to take a look at the series 
> (which
>> unfortunately may take a few days to get to).
> 
> thanks for your review. Any comment, I will reply to your emails ASAP.

Thanks. It would however have been nice if you addressed the
implied question (regarding the reason) right away.

Jan


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