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[35.247.111.240]) by smtp.gmail.com with ESMTPSA id ft3sm5556349pjb.54.2021.04.22.11.11.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Apr 2021 11:11:50 -0700 (PDT) Date: Thu, 22 Apr 2021 18:11:46 +0000 From: Sean Christopherson To: Paolo Bonzini Cc: Dave Hansen , Andy Lutomirski , Peter Zijlstra , Wei Huang , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Borislav Petkov , Tom Lendacky , Brijesh Singh Subject: Re: [PATCH v5 03/15] KVM: SVM: Disable SEV/SEV-ES if NPT is disabled Message-ID: References: <20210422021125.3417167-1-seanjc@google.com> <20210422021125.3417167-4-seanjc@google.com> <5e8a2d7d-67de-eef4-ab19-33294920f50c@redhat.com> <882d8bb4-8d40-1b4d-0742-4a4f2c307e5b@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <882d8bb4-8d40-1b4d-0742-4a4f2c307e5b@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 22, 2021, Paolo Bonzini wrote: > On 22/04/21 18:15, Sean Christopherson wrote: > > > Support for 5-level page tables on NPT is not hard to fix and could be > > > tested by patching QEMU. However, the !NPT case would also have to be fixed > > > by extending the PDP and PML4 stacking trick to a PML5. > > Isn't that backwards? It's the nested NPT case that requires the stacking trick. > > When !NPT is disabled in L0 KVM, 32-bit guests are run with PAE paging. Maybe > > I'm misunderstanding what you're suggesting. > > Yes, you're right. NPT is easy but we would have to guess what the spec > would say about MAXPHYADDR, while nNPT would require the stacking of a PML5. > Either way, blocking KVM is the easiest thing todo. How about I fold that into the s/lm_root/pml4_root rename[*]? I.e. make the blocking of PML5 a functional change, and the rename an opportunistic change? [*] https://lkml.kernel.org/r/20210318201131.3242619-1-seanjc@google.com