Re: [Xen-devel] [PATCH v2] x86/domain_page: implement pure per-vCPU mapping infrastructure

[Jan Beulich <jbeulich@xxxxxxxx>]

On 21.02.2020 13:52, Xia, Hongyan wrote:
> On Fri, 2020-02-21 at 11:50 +0000, Wei Liu wrote:
>> On Thu, Feb 06, 2020 at 06:58:23PM +0000, Hongyan Xia wrote:
>>> +    if ( hashmfn != mfn && !vcache->refcnt[idx] )
>>> +        __clear_bit(idx, vcache->inuse);
>>
>> Also, please flush the linear address here and the other __clear_bit
>> location.
> 
> I flush when a new entry is taking a slot. Yeah, it's probably better
> to flush earlier whenever a slot is no longer in use.

Question is whether such individual flushes aren't actually
more overhead than a single flush covering all previously
torn down entries, done at suitable points (see the present
implementation).

Jan

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