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:
> > I agree that it _shouldn't_ end up emulating -- but the shadow page fault
> > routine has a ton of code paths that I've never managed to fully grok
> >
> > (As an aside, I've previously looked at other cases where the shadow code
> > ends up emulating instructions that are unexpected that cause VMs to
> hang
> > because the shadow module doesn't have a proper implementation of the
> > x86_emulate callbacks... e.g. if you try to run the old MS Virtual Server
> > product inside a Xen VM that has logdirty enabled it _will_ hard hang).
> 
> Perhaps that's then what really needs fixing?
> 

Well, I don't disagree but I also think the two problems are orthogonal -- the 
shadow use of x86_emulate is incomplete but every use of x86_emulate suffers 
from the problem that copies to and from memory are not following the 
definition of the x86 architecture.

I previously looked at fixing the shadow use of x86_emulate but it's a big job 
that I don't have the expertise or time to address.

Simon

> Jan


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