Re: [Xen-devel] [PATCH] ARM: cache coherence problem in guestcopy.c

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2013-06-20 at 08:34 +0000, Jaeyong Yoo wrote:
> > On Tue, 2013-06-18 at 13:18 +0100, Ian Campbell wrote:
> > > On Tue, 2013-06-18 at 12:05 +0000, Jaeyong Yoo wrote:
> > > > > We were also speculating that we probably want some DMBs in
> > > > > context_switch_{from,to} as well as at return_to_guest.
> > > > 
> > > > Actually, I just learned ReOrder Buffer, and it looks like so.
> > 
> > Does this patch help with the issue you are seeing?
> 
> I tried the combinations and it does not work.

As an experiment can you try the same patch with dsb instead of dmb
throughout?

Could you also try the patch from my series "xen: arm: map normal memory
as inner shareable, reduce scope of various barriers" in
<1372435809.8976.169.camel@xxxxxxxxxxxxxxxxxxxxxx>, speaking with ARM
they reminded me that Xen currently uses Outer-shareable mappings while
Linux uses Inner-, which is more than likely the root cause of the issue
you are seeing. You probably want the dmb() patch as well to avoid
speculative fetches.

Ian.


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