Re: [Xen-devel] [PATCH] x86/HVM: use single (atomic) MOV for aligned emulated writes

[Jason Andryuk <jandryuk@xxxxxxxxx>]

On Tue, Jan 14, 2020 at 4:28 AM Jan Beulich <jbeulich@xxxxxxxx> wrote:
>
> On 13.01.2020 20:40, Jason Andryuk wrote:
> > On Fri, Dec 27, 2019 at 11:09 AM Andrew Cooper
> > <andrew.cooper3@xxxxxxxxxx> wrote:
> >>
> >> On 20/12/2019 16:23, Jan Beulich wrote:
> >>> On 16.09.2019 11:40, Jan Beulich wrote:
> >>>> Using memcpy() may result in multiple individual byte accesses
> >>>> (dependening how memcpy() is implemented and how the resulting insns,
> >>>> e.g. REP MOVSB, get carried out in hardware), which isn't what we
> >>>> want/need for carrying out guest insns as correctly as possible. Fall
> >>>> back to memcpy() only for accesses not 2, 4, or 8 bytes in size.
> >>>>
> >>>> Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> >>>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> >>
> >> Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> >
> > Should xen/arch/x86/mm/shadow/hvm.c:hvm_emulate_write() be similarly 
> > changed?
>
> Probably. Care to make a patch?

Sure :)

-Jason

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