Re: [PATCH v3 04/19] KVM: MMU: cache mmio info on page fault path

Xiao Guangrong
2011-07-06T01:15:34Z

On 07/06/2011 03:04 AM, Marcelo Tosatti wrote:
return 0;
>>
>> /* mmio */
>> - if (is_error_pfn(pfn))
>> - return kvm_handle_bad_page(vcpu->kvm, walker.gfn, pfn);
>> + if (is_error_pfn(pfn)) {
>> + unsigned access = walker.pte_access;
>> + bool dirty = is_dirty_gpte(walker.ptes[walker.level - 1]);
>> +
>> + if (dirty)
>> + access &= ~ACC_WRITE_MASK;
>> +
>> + return kvm_handle_bad_page(vcpu, mmu_is_nested(vcpu) ? 0 :
>> + addr, access, walker.gfn, pfn);
>> + }
>
> Don't get this... if guest pte is dirty you cache without allowing
> write access? Why?
>

Ah, sorry, the logic should be: if pte is not diry, clear write access,
will fix it. Thanks, Marcelo!