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SubjectRe: [PATCH 1/4] KVM: MMU: fix forgot reserved bits check in speculative path
On 07/14/2010 04:24 PM, Xiao Guangrong wrote:
>
> Avi Kivity wrote:
>
>
>>> +
>>> + if (!!is_pae(vcpu) != sp->role.cr4_pae ||
>>> + is_nx(vcpu) != sp->role.nxe)
>>> + continue;
>>> +
>>>
>>>
>> Do we also need to check cr0.wp? I think so.
>>
> I think it's not too bad since we just decrease the access right, for example,
> we mark the mapping readonly for cr0.wp=0's page, the later write-access will
> cause #PF, and the read-access is OK.
>

If current cr0.wp=0 and sp->role.cr0_wp=1, that's fine, but the other
way round can relax permissions too much, marking a kernel page writeable.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.



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