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Re: [Xen-devel] [PATCH v6 05/10] Clear AC bit in RFLAGS to protect Xen itself by SMAP

>>> On 08.05.14 at 08:49, <feng.wu@xxxxxxxxx> wrote:
>> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
>> >>> On 08.05.14 at 04:02, <feng.wu@xxxxxxxxx> wrote:
>> > Sure, thanks for the suggestion! I will pass 0 to SAVE_ALL.
>> > My point is that ASM_STAC should be deferred as much as possible.
>> There's no point in deferring it as much as possible if you don't CLAC
>> earlier on. In fact I'm inclined to ask to make the SAVE_ALL parameter
>> a tristate, allowing both CLAC and STAC to be done right there.
> Currently, there is only one place where we need to set AC around SAVE_ALL, 
> it is double_fault.
> Do we really need to make SAVE_ALL that way?

Note that I wrote "I'm inclined to ask ...", not "I'd like to ask ...", i.e.
if you feel uncomfortable with this, I'm still fine with leaving the macro
as is. But my argument stands that deferring STAC here as much as
possible is pointless.


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