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([2001:b07:6468:f312:63a7:c72e:ea0e:6045]) by smtp.gmail.com with ESMTPSA id c17sm844174edu.11.2021.08.10.02.25.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 10 Aug 2021 02:25:28 -0700 (PDT) Subject: Re: [PATCH v2 1/3] KVM: x86: Allow CPU to force vendor-specific TDP level To: Yu Zhang , Sean Christopherson Cc: Wei Huang , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, vkuznets@redhat.com, wanpengli@tencent.com, jmattson@google.com, joro@8bytes.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com References: <20210808192658.2923641-1-wei.huang2@amd.com> <20210808192658.2923641-2-wei.huang2@amd.com> <20210809035806.5cqdqm5vkexvngda@linux.intel.com> <20210809042703.25gfuuvujicc3vj7@linux.intel.com> <73bbaac0-701c-42dd-36da-aae1fed7f1a0@amd.com> <20210809064224.ctu3zxknn7s56gk3@linux.intel.com> <20210810074037.mizpggevgyhed6rm@linux.intel.com> From: Paolo Bonzini Message-ID: <0ac41a07-beeb-161e-9e5d-e45477106c01@redhat.com> Date: Tue, 10 Aug 2021 11:25:27 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210810074037.mizpggevgyhed6rm@linux.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 10/08/21 09:40, Yu Zhang wrote: > About "host can't easily mirror L1's desired paging mode", could you please elaborate? > Thanks! Shadow pgae tables in KVM will always have 3 levels on 32-bit machines and 4/5 levels on 64-bit machines. L1 instead might have any number of levels from 2 to 5 (though of course not more than the host has). Therefore, when shadowing 32-bit NPT page tables, KVM has to add extra fixed levels on top of those that it's shadowing. See mmu_alloc_direct_roots for the code. Paolo