RE: [PATCH] x86emul: fix FXRSTOR test for most AMD CPUs

[Paul Durrant <xadimgnik@xxxxxxxxx>]

> -----Original Message-----
> From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Sent: 06 July 2020 16:47
> To: Jan Beulich <jbeulich@xxxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Wei Liu <wl@xxxxxxx>; Roger Pau Monné <roger.pau@xxxxxxxxxx>; Paul 
> Durrant <paul@xxxxxxx>
> Subject: Re: [PATCH] x86emul: fix FXRSTOR test for most AMD CPUs
> 
> On 06/07/2020 16:14, Jan Beulich wrote:
> > AMD CPUs that we classify as X86_BUG_FPU_PTRS don't touch the selector/
> > offset portion of the save image during FXSAVE unless an unmasked
> > exception is pending. Hence the selector zapping done between the
> > initial FXSAVE and the emulated FXRSTOR needs to be mirrored onto the
> > second FXSAVE, output of which gets fed into memcmp() to compare with
> > the input image.
> >
> > Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Tested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Release-acked-by: Paul Durrant <paul@xxxxxxx>