Re: [PATCH 1/10] KVM MMU: fix for calculating gpa in invlpg code

Avi Kivity
2010-04-23T12:11:42Z

On 04/23/2010 03:05 PM, Xiao Guangrong wrote:
>
>
>>> @@ -478,9 +478,14 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu,
>>> gva_t gva)
>>> ((level == PT_DIRECTORY_LEVEL&& is_large_pte(*sptep))) ||
>>> ((level == PT_PDPE_LEVEL&& is_large_pte(*sptep)))) {
>>> struct kvm_mmu_page *sp = page_header(__pa(sptep));
>>> + int offset = 0;
>>> +
>>> + if (PTTYPE == 32)
>>> + offset = sp->role.quadrant<< PT64_LEVEL_BITS;;
>>>
>>>
>> Wrong for PT_DIRECTORY_LEVEL (should be q<< 8). Also, too many
>> semicolons.
>>
>>
> I guess you mean 'PT64_LEVEL_BITS' not 'PT_DIRECTORY_LEVEL' here :-)
>

No, I mean if level == PT_DIRECTORY_LEVEL, then we want role.quadrant <<
8, not 9.

> It should be q<< 8 here? it hardly understand, take leve = 1 for example,
> 32-bit guest PTE page table mapping range is 2^(10+12), PAE's PTE page table
> mapping range is 2^(9+12),

For level == PT_DIRECTORY_LEVEL, quadrant is in the range 0..3. Each sp
maps 1GB, while the guest page table maps 4GB. So the upper two bits
become the quadrant.

> so, i think it's quadrant<< 9 here, and other
> function like FNAME(prefetch_page), FNAME(sync_page) also are q<< 9
>

They only work for PT_PAGE_TABLE_LEVEL, so for them 9 is correct.

--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.