Messages in this thread | | | Date | Tue, 23 Aug 2011 04:21:05 +0800 | From | Xiao Guangrong <> | Subject | Re: [PATCH 03/11] KVM: x86: retry non-page-table writing instruction |
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On 08/23/2011 03:59 AM, Marcelo Tosatti wrote:
>> + if (!vcpu->arch.mmu.direct_map && !mmu_is_nested(vcpu)) >> + gpa = kvm_mmu_gva_to_gpa_write(vcpu, cr2, NULL); > > Why write? >
Since the fault is caused by page table written, and the 'gpa' can be written after instruction is retied.
>> + kvm_mmu_unprotect_page(vcpu->kvm, gpa >> PAGE_SHIFT); >> + >> + /* >> + * The shadow pages have been zapped, then we call the page >> + * fault path to change the mapping to writable. >> + */ >> + vcpu->arch.mmu.page_fault(vcpu, cr2, PFERR_WRITE_MASK, true); > > I don't see why is this necessary. Just allowing the instruction to > proceed should be enough? >
It used to avoid later VM-exit, since we will retry the instruction but the mapped is still read-only. So we can it to let the mapping become writable to avoid page fault again.
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