Messages in this thread | | | Subject | Re: [PATCH v2 1/3] kvm: svm: Add support for additional SVM NPF error codes | From | Brijesh Singh <> | Date | Fri, 4 Aug 2017 09:23:29 -0500 |
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Hi Paolo,
On 08/04/2017 09:05 AM, Paolo Bonzini wrote: > On 04/08/2017 02:30, Brijesh Singh wrote: >> >> >> On 8/2/17 5:42 AM, Paolo Bonzini wrote: >>> On 01/08/2017 15:36, Brijesh Singh wrote: >>>>> The flow is: >>>>> >>>>> hardware walks page table; L2 page table points to read only memory >>>>> -> pf_interception (code = >>>>> -> kvm_handle_page_fault (need_unprotect = false) >>>>> -> kvm_mmu_page_fault >>>>> -> paging64_page_fault (for example) >>>>> -> try_async_pf >>>>> map_writable set to false >>>>> -> paging64_fetch(write_fault = true, map_writable = false, >>>>> prefault = false) >>>>> -> mmu_set_spte(speculative = false, host_writable = false, >>>>> write_fault = true) >>>>> -> set_spte >>>>> mmu_need_write_protect returns true >>>>> return true >>>>> write_fault == true -> set emulate = true >>>>> return true >>>>> return true >>>>> return true >>>>> emulate >>>>> >>>>> Without this patch, emulation would have called >>>>> >>>>> ..._gva_to_gpa_nested >>>>> -> translate_nested_gpa >>>>> -> paging64_gva_to_gpa >>>>> -> paging64_walk_addr >>>>> -> paging64_walk_addr_generic >>>>> set fault (nested_page_fault=true) >>>>> >>>>> and then: >>>>> >>>>> kvm_propagate_fault >>>>> -> nested_svm_inject_npf_exit >>>>> >>>> maybe then safer thing would be to qualify the new error_code check with >>>> !mmu_is_nested(vcpu) or something like that. So that way it would run on >>>> L1 guest, and not the L2 guest. I believe that would restrict it avoid >>>> hitting this case. Are you okay with this change ? >>> Or check "vcpu->arch.mmu.direct_map"? That would be true when not using >>> shadow pages. >> >> Yes that can be used. > > Are you going to send a patch for this? >
Yes. I should be posting it by Monday or Tuesday - need sometime to verify it.
-Brijesh
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