From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bandan Das Subject: Re: [PATCH v4 3/3] KVM: nVMX: Emulate EPTP switching for the L1 hypervisor Date: Wed, 19 Jul 2017 13:54:46 -0400 Message-ID: References: <20170710204936.4001-1-bsd@redhat.com> <20170710204936.4001-4-bsd@redhat.com> <2d50ebc4-9328-ce08-b55b-6a331ee13cc3@redhat.com> <20170711193235.GE3326@potion> <20170711202118.GC28875@potion> <20170719093036.GA13079@potion> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Cc: David Hildenbrand , kvm@vger.kernel.org, pbonzini@redhat.com, linux-kernel@vger.kernel.org To: Radim =?utf-8?B?S3LEjW3DocWZ?= Return-path: In-Reply-To: <20170719093036.GA13079@potion> ("Radim \=\?utf-8\?B\?S3LEjW0\=\?\= \=\?utf-8\?B\?w6HFmSIncw\=\=\?\= message of "Wed, 19 Jul 2017 11:30:37 +0200") Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org Radim Krčmář writes: > 2017-07-17 13:58-0400, Bandan Das: >> Radim Krčmář writes: >> ... >>>> > and no other mentions of a VM exit, so I think that the VM exit happens >>>> > only under these conditions: >>>> > >>>> > — The EPT memory type (bits 2:0) must be a value supported by the >>>> > processor as indicated in the IA32_VMX_EPT_VPID_CAP MSR (see >>>> > Appendix A.10). >>>> > — Bits 5:3 (1 less than the EPT page-walk length) must be 3, indicating >>>> > an EPT page-walk length of 4; see Section 28.2.2. >>>> > — Bit 6 (enable bit for accessed and dirty flags for EPT) must be 0 if >>>> > bit 21 of the IA32_VMX_EPT_VPID_CAP MSR (see Appendix A.10) is read >>>> > as 0, indicating that the processor does not support accessed and >>>> > dirty flags for EPT. >>>> > — Reserved bits 11:7 and 63:N (where N is the processor’s >>>> > physical-address width) must all be 0. >>>> > >>>> > And it looks like we need parts of nested_ept_init_mmu_context() to >>>> > properly handle VMX_EPT_AD_ENABLE_BIT. >>>> >>>> I completely ignored AD and the #VE sections. I will add a TODO item >>>> in the comment section. >>> >>> AFAIK, we don't support #VE, but AD would be nice to handle from the >>> beginning. (I think that caling nested_ept_init_mmu_context() as-is >>> isn't that bad.) >> >> I went back to the spec to take a look at the AD handling. It doesn't look >> like anything needs to be done since nested_ept_init_mmu_context() is already >> being called with the correct eptp in prepare_vmcs02 ? Anything else that >> needs to be done for AD handling in vmfunc context ? > > AD is decided by EPTP bit 6, so it can be toggled by EPTP switching and > we don't call prepare_vmcs02() after emulating VMFUNC vm exit. > We want to forward the new AD configuration to KVM's MMU. Thanks, I had incorrectly assumed that prepare_vmcs02 will be called after an exit unconditionally. I will work something up soon. Bandan