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

[Sengul Thomas <thomas.sengul@xxxxxxxxx>]

On Tue, Jul 2, 2013 at 6:38 PM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> 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?

I tried several ways to recreate the problem I was having, but I
failed. I was having
that problem with some printks place to place, and sadly, I don't
remember the printk positions.
I'm sorry.

Jaeyong

>
> 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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