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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id x7sm1263870ede.86.2021.09.22.07.07.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 22 Sep 2021 07:07:15 -0700 (PDT) Subject: Re: [PATCH] KVM: nVMX: Filter out all unsupported controls when eVMCS was activated To: Vitaly Kuznetsov , Sean Christopherson Cc: kvm@vger.kernel.org, Wanpeng Li , Jim Mattson , linux-kernel@vger.kernel.org References: <20210907163530.110066-1-vkuznets@redhat.com> <87v93a2pu9.fsf@vitty.brq.redhat.com> From: Paolo Bonzini Message-ID: <6e97f33c-e4d4-5669-c642-a904c9e22a8d@redhat.com> Date: Wed, 22 Sep 2021 16:07:13 +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: <87v93a2pu9.fsf@vitty.brq.redhat.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: linux-kernel@vger.kernel.org On 09/09/21 09:03, Vitaly Kuznetsov wrote: > Sean Christopherson writes: > >> On Tue, Sep 07, 2021, Vitaly Kuznetsov wrote: >>> Let's be bold this time and instead of playing whack-a-mole just filter out >>> all unsupported controls from VMX MSRs. >> >> Out of curiosity, why didn't we do this from the get-go? > > We actually did, the initial implementation (57b119da3594f) was > filtering out everything but then things changed in "only clear controls > which are known to cause issues" (31de3d2500e4). I forgot everything > already but was able to google this suggestion from Paolo: > > https://www.lkml.org/lkml/2020/1/22/1108 The doubt was whether userspaces could be enabling eVMCS blindly, and thus would lose features for Linux guests. Paolo