Avi Kivity wrote:
> On 04/25/2010 10:00 AM, Xiao Guangrong wrote:
>> If the guest is 32-bit, we should use 'quadrant' to adjust gpa
>> offset
>>
>> Changlog v2:
>> - when level is PT_DIRECTORY_LEVEL, the 'offset' should be
>> 'role.quadrant<< 8', thanks Avi for point it out
>>
>> Signed-off-by: Xiao Guangrong<xiaoguangrong@xxxxxxxxxxxxxx>
>> ---
>> arch/x86/kvm/paging_tmpl.h | 13 +++++++++++--
>> 1 files changed, 11 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
>> index d0cc07e..83cc72f 100644
>> --- a/arch/x86/kvm/paging_tmpl.h
>> +++ b/arch/x86/kvm/paging_tmpl.h
>> @@ -478,9 +478,18 @@ 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) {
>> + if (level == PT_DIRECTORY_LEVEL)
>> + offset = PAGE_SHIFT - 4;
>> + else
>> + offset = PT64_LEVEL_BITS;
>> + offset = sp->role.quadrant<< offset;
>> + }
>>
>
> The calculation is really
>
> shift = (PT32_LEVEL_BITS - PT64_LEVEL_BITS) * level;
>
So, the offset is q << (PAGE_SHIFT - (PT32_LEVEL_BITS - PT64_LEVEL_BITS) * level - 2)?
As my origin thinking, for level = 2, one gfn has 4 shadow pages, so
every shadow page occupies PAGE_SIZE / 4, and sizeof(pt_element_t) is 4
in 32-bit guest, so the offset is:
q * (PAGE_SIZE/4/4) = q << (PAGE_SHIFT - 2 -2)
Obviously, my code is really ugly than your :-)
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