Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755690AbdDLXC5 (ORCPT ); Wed, 12 Apr 2017 19:02:57 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36850 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754419AbdDLXCy (ORCPT ); Wed, 12 Apr 2017 19:02:54 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 0E425C059744 Authentication-Results: ext-mx08.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx08.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=bsd@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 0E425C059744 From: Bandan Das To: Paolo Bonzini Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, david@redhat.com Subject: Re: [PATCH 4/6] kvm: nVMX: support EPT accessed/dirty bits References: <1490867732-16743-1-git-send-email-pbonzini@redhat.com> <1490867732-16743-5-git-send-email-pbonzini@redhat.com> <317734077.12913155.1491954869446.JavaMail.zimbra@redhat.com> Date: Wed, 12 Apr 2017 19:02:50 -0400 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Wed, 12 Apr 2017 23:02:54 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2376 Lines: 64 Paolo Bonzini writes: > ----- Original Message ----- >> From: "Bandan Das" >> To: "Paolo Bonzini" >> Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, david@redhat.com >> Sent: Wednesday, April 12, 2017 7:35:16 AM >> Subject: Re: [PATCH 4/6] kvm: nVMX: support EPT accessed/dirty bits >> >> Paolo Bonzini writes: >> ... >> > accessed_dirty = have_ad ? PT_GUEST_ACCESSED_MASK : 0; >> > + >> > + /* >> > + * FIXME: on Intel processors, loads of the PDPTE registers for PAE >> > paging >> > + * by the MOV to CR instruction are treated as reads and do not cause the >> > + * processor to set the dirty flag in tany EPT paging-structure entry. >> > + */ >> >> Minor typo: "in any EPT paging-structure entry". >> >> > + nested_access = (have_ad ? PFERR_WRITE_MASK : 0) | PFERR_USER_MASK; >> > + >> > pt_access = pte_access = ACC_ALL; >> > ++walker->level; >> > >> > @@ -338,7 +337,7 @@ static int FNAME(walk_addr_generic)(struct guest_walker >> > *walker, >> > walker->pte_gpa[walker->level - 1] = pte_gpa; >> > >> > real_gfn = mmu->translate_gpa(vcpu, gfn_to_gpa(table_gfn), >> > - PFERR_USER_MASK|PFERR_WRITE_MASK, >> > + nested_access, >> > &walker->fault); >> >> I can't seem to understand the significance of this change (or for that >> matter what was before this change). >> >> mmu->translate_gpa() just returns gfn_to_gpa(table_gfn), right ? > > For EPT it is, you're right it's fishy. The "nested_access" should be > computed in translate_nested_gpa, which is where kvm->arch.nested_mmu > (non-EPT) requests to access kvm->arch.mmu (EPT). Thanks for the clarification. Is it the case when L1 runs L2 without EPT ? I can't figure out the case where translate_nested_gpa will actually be called. FNAME(walk_addr_nested) calls walk_addr_generic with &vcpu->arch.nested_mmu and init_kvm_nested_mmu() sets gva_to_gpa() with the appropriate "_nested" functions. But the gva_to_gpa() pointers don't seem to get invoked at all for the nested case. BTW, just noticed that setting PFERR_USER_MASK is redundant since translate_nested_gpa does it too. Bandan > In practice we need to define a new function > vcpu->arch.mmu.gva_to_gpa_nested that computes the nested_access > and calls cpu->arch.mmu.gva_to_gpa. > > Thanks, > > Paolo