Re: [PATCH] KVM: SVM: obey guest PAT

[Radim KrÄmÃÅ]

2017-10-26 09:13+0200, Paolo Bonzini:
> For many years some users of assigned devices have reported worse
> performance on AMD processors with NPT than on AMD without NPT,
> Intel or bare metal.
> 
> The reason turned out to be that SVM is discarding the guest PAT
> setting and uses the default (PA0=PA4=WB, PA1=PA5=WT, PA2=PA6=UC-,
> PA3=UC).  The guest might be using a different setting, and
> especially might want write combining but isn't getting it
> (instead getting slow UC or UC- accesses).
> 
> Thanks a lot to geoff@xxxxxxxxxxxxxxx for noticing the relation
> to the g_pat setting.  The patch has been tested also by a bunch
> of people on VFIO users forums.
> 
> Fixes: 709ddebf81cb40e3c36c6109a7892e8b93a09464
> Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=196409
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>

Applied, thanks.