On 11/28/2012 10:12 PM, Gleb Natapov wrote: > On Tue, Nov 27, 2012 at 11:30:24AM +0800, Xiao Guangrong wrote: >> On 11/27/2012 06:41 AM, Marcelo Tosatti wrote: >> >>>> >>>> - return false; >>>> +again: >>>> + page_fault_count = ACCESS_ONCE(vcpu->kvm->arch.page_fault_count); >>>> + >>>> + /* >>>> + * if emulation was due to access to shadowed page table >>>> + * and it failed try to unshadow page and re-enter the >>>> + * guest to let CPU execute the instruction. >>>> + */ >>>> + kvm_mmu_unprotect_page(vcpu->kvm, gpa_to_gfn(gpa)); >>>> + emulate = vcpu->arch.mmu.page_fault(vcpu, cr3, PFERR_WRITE_MASK, false); >>> >>> Can you explain what is the objective here? >>> >> >> Sure. :) >> >> The instruction emulation is caused by fault access on cr3. After unprotect >> the target page, we call vcpu->arch.mmu.page_fault to fix the mapping of cr3. >> if it return 1, mmu can not fix the mapping, we should report the error, >> otherwise it is good to return to guest and let it re-execute the instruction >> again. >> >> page_fault_count is used to avoid the race on other vcpus, since after we >> unprotect the target page, other cpu can enter page fault path and let the >> page be write-protected again. >> >> This way can help us to detect all the case that mmu can not be fixed. >> > Can you write this in a comment above vcpu->arch.mmu.page_fault()? Okay, if Marcelo does not object this way. :) -- 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
