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Re: [Xen-devel] Intermittent fatal page fault with XEN 4.3.1 (Centos 6.3 DOM0 with linux kernel 3.10.16.)

On Nov 7, 2013, at 8:53 AM, Jan Beulich <JBeulich@xxxxxxxx>

>>>> On 07.11.13 at 17:02, <Jeff_Zimmerman@xxxxxxxxxx> wrote:
>> On Nov 7, 2013, at 7:57 AM, Jan Beulich <JBeulich@xxxxxxxx>
>> wrote:
>>>>>> On 07.11.13 at 16:41, <Jeff_Zimmerman@xxxxxxxxxx> wrote:
>>>> On Nov 7, 2013, at 1:30 AM, Ian Campbell <Ian.Campbell@xxxxxxxxxx>  wrote:
>>>>> I was also wondering about the behaviour of using vmx instructions in a
>>>>> guest despite vmx not being visible in cpuid...
>>>> We have found in our situation this is exactly the case. To verify we 
>>>> wrote 
>>>> some
>>>> test code that makes vmx calls without checking cupid. On bare hardware 
>>>> the 
>>>> program
>>>> executes as expected. In a VM on Xen it causes the hypervisor to panic.
>>> You trying it doesn't yet imply that Windows also does so.
>>> Also, you say "program" - are you using these from user mode code?
>> Yes, from windows run as a privileged user. Windows XP sp3 can cause the 
>> crash.
>> It seems windows 7 has better security, we cannot crash the system from a 
>> win7 guest.
> Which is sort of odd. Anyway - care to try the attached patch?
> Jan
> <xsa75.patch>

Just tried your patch. It seems to mitigate the problem.
Thanks!  -jeff

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