Re: [Xen-devel] [PATCH 1/2] Revert "xen: properly account for _PAGE_NUMA during xen pte translations"

[David Sutton <kantras@xxxxxxxxx>]

David,

On Tue, Mar 25, 2014 at 12:13 PM, David Vrabel <david.vrabel@xxxxxxxxxx> wrote:

On 25/03/14 15:28, David Sutton wrote:
> David,
>
>> This reverts commit a9c8e4beeeb64c22b84c803747487857fe424b68.
>>
> Please note: this particular patch also helped to resolve an issue
> reported by some of the people using the xen package under Arch Linux,
> where they would see stability issues running certain software
> (particularly firefox) under dom0 - the software would start crashing
> under relatively light usage, with a kernel BUG message.

We are aware that Xen PV guests will not work if CONFIG_NUMA_BALANCING
is enabled with this revert.  But that patch introduced fundamental
breakage to how a guest must read/write non-present page tables entries
which caused even worse breakage.

Understood - I just wanted to make sure that another symptom of the issue was known in case it came up - some people read the issue description and were confused as they weren't using any PV guests, only seeing the specific application crashes under dom0
 

I suspect that the problematic patch 1667918b6483 ("mm: numa: clear numa
hinting information on mprotect") is not needed on x86 and could be
safely reverted as a temporarily fix.

David

Regards,

  David

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