On Tue, Aug 23, 2011 at 04:21:05AM +0800, Xiao Guangrong wrote: > 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. Its not like this case is performance sensitive. Usually optimizing things without the need for it leads to bad results. So please drop this. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
