Re: [Xen-devel] [PATCH] x86/xsave: Remove xfeat_mask checking from validate_xstate()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.06.14 at 12:07, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 02/06/14 07:43, Jan Beulich wrote:
>>>>> On 30.05.14 at 13:57, <andrew.cooper3@xxxxxxxxxx> wrote:
>>> What further sanity checking would be wanted/needed?
>>>
>>> The sending Xen must have gotten this correct else it wouldn't have an 
>>> xsave area to send in the first place.  If the receiving the Xen found 
>>> parts it didn't like, the local validity checks would fail.
>>>
>>> As far as I can see, the only case this might do something unexpected is 
>>> if the individual xfeature_mask got changed on transit, at which point 
>>> the receiving Xen would fail the xsave load, despite the xsave area 
>>> being valid for the current cpu.
>> Whether the loading would fail really depends on what exactly became
>> corrupted.
> 
> The current behaviour is that the load would fail, as validate_xstate()
> would fail.

Oh, then we meant different things with "load" (I was assuming you
meant the actual xrstor).

>> But in the end the question is - are you intending to no longer
>> communicate this bit of information in the v2 migration stream?
> 
> Ideally I would like to cease communicating this in the v2 stream.

Okay, on that basis I'm willing to take the patch; any chance you
could add a note to this effect to the commit message?

Jan


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