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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id d15sm2704139edu.86.2021.04.22.10.08.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 22 Apr 2021 10:08:06 -0700 (PDT) Subject: Re: [PATCH v5 03/15] KVM: SVM: Disable SEV/SEV-ES if NPT is disabled To: Sean Christopherson 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 References: <20210422021125.3417167-1-seanjc@google.com> <20210422021125.3417167-4-seanjc@google.com> <5e8a2d7d-67de-eef4-ab19-33294920f50c@redhat.com> From: Paolo Bonzini Message-ID: <882d8bb4-8d40-1b4d-0742-4a4f2c307e5b@redhat.com> Date: Thu, 22 Apr 2021 19:08:05 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Paolo