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

["Wu, Feng" <feng.wu@xxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Thursday, May 08, 2014 2:41 PM
> To: Wu, Feng
> Cc: Andrew Cooper; ian.campbell@xxxxxxxxxx; Dong, Eddie; Nakajima, Jun; Tian,
> Kevin; xen-devel@xxxxxxxxxxxxx
> Subject: RE: [PATCH v6 05/10] Clear AC bit in RFLAGS to protect Xen itself by
> SMAP
> 
> >>> On 08.05.14 at 04:02, <feng.wu@xxxxxxxxx> wrote:
> >> From: Andrew Cooper [mailto:amc96@xxxxxxxxxxxxxxxx] On Behalf Of
> >> I am not fussed where exactly the STAC goes in the entry point, but
> >> don't leave a CLAC in the SAVE_ALL.
> >
> > 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.
> 
> Jan

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?

Thanks,
Feng

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