Re: [Xen-devel] Possible issue with x86_emulate when writing results back to memory

[Simon Graham <simon.graham@xxxxxxxxxx>]

> >>> On 09.01.14 at 18:33, Simon Graham <simon.graham@xxxxxxxxxx> wrote:
> >> __hvm_copy() is probably too low to be thinking about this.  There are
> >> many things such as grant_copy() which do not want "hardware like" copy
> >> properties, preferring instead to have less overhead.
> >>
> >
> > Yeah... I'll rework the patch to do this...
> 
> Looking a little more closely, hvm_copy_{to,from}_guest_virt()
> are what you want to have the adjusted behavior. That way
> you'd in particular not touch the behavior of the more generic
> copying routines copy_{to,from}_user_hvm(). And adjusting
> the behavior would seem to be doable cleanly by adding e.g.
> HVMCOPY_atomic as a new flag, thus informing __hvm_copy()
> to not use memcpy().
> 

Thanks -- I was coming to the same conclusion slowly too! Although I think I 
might call it HVMCOPY_emulate rather than atomic since it's not the case that 
the entire copy is atomic...

Now I just have to figure out why the shadow code doesn't use the hvm copy_to_ 
routine...

> Jan


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