Messages in this thread | | | Date | Mon, 26 Apr 2010 11:10:15 +0800 | From | Xiao Guangrong <> | Subject | Re: [PATCH v2 1/10] KVM MMU: fix for calculating gpa in invlpg code |
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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@cn.fujitsu.com> >> --- >> 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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