Re: [Xen-devel] [PATCH 3 of 6] xen/pat: After suspend re-write PAT if BIOS changed it

[Tom Goetz <tom.goetz@xxxxxxxxxxxxxxxxxxx>]

On Apr 2, 2012, at 11:28 AM, Konrad Rzeszutek Wilk wrote:

> On Mon, Mar 26, 2012 at 09:50:11AM +0100, Jan Beulich wrote:
>>>>> On 24.03.12 at 18:41, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> 
>>>>> wrote:
>>> # HG changeset patch
>>> # User Simon Graham <simon.graham@xxxxxxxxxxxxxxxxxxx>
>>> # Date 1332610898 14400
>>> # Node ID 75798a472b1a9121adda166b6fd05ba8473a44f0
>>> # Parent  d097c3ba42f601af65b53a0c84973855aab64aa9
>>> xen/pat: After suspend re-write PAT if BIOS changed it.
>>> 
>>> Certain AMD machines (this was a MSI or GigaBYTE BIOS) after resume
>>> would reset the PAT MSR causing rather weird issues - where
>>> the pages would (say they would be set to WC) would end up with the
>>> wrong type (as they would use the BIOS PAT instead of the one set by
>>> the hypervisor).
>> 
>> There's a write of the PAT MSR already at the end of
>> restore_rest_processor_state() - are you saying this doesn't do
>> what is needed? Also note that this is properly gated by a check
>> of cpu_has_pat (other than the patch here does).
> 
> Let me double-check with folks at VirtualComputer - but they had
> experienced this with Xen 4.0 (I think) and the c/s 19167 certainly
> was in there.


We've been carrying this patch since before Xen 3.4 days. Given Jan's 
information we will remove it, retest, and get back to you.


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel