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([2001:b07:6468:f312:59c7:c3ee:2dec:d2b4]) by smtp.gmail.com with ESMTPSA id x6sm6698593wrr.6.2020.02.18.08.13.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 Feb 2020 08:13:28 -0800 (PST) Subject: Re: [PATCH RFC] target/i386: filter out VMX_PIN_BASED_POSTED_INTR when enabling SynIC To: Vitaly Kuznetsov , qemu-devel@nongnu.org References: <20200218144415.94722-1-vkuznets@redhat.com> From: Paolo Bonzini Message-ID: <9b4b46c2-e2cf-a3d5-70e4-c8772bf6734f@redhat.com> Date: Tue, 18 Feb 2020 17:13:26 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <20200218144415.94722-1-vkuznets@redhat.com> Content-Language: en-US X-MC-Unique: Pf4Kw3SROU2UMHlIdD3egw-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.61 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Eduardo Habkost , kvm@vger.kernel.org, Marcelo Tosatti , Liran Alon , Roman Kagan , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 18/02/20 15:44, Vitaly Kuznetsov wrote: > Signed-off-by: Vitaly Kuznetsov > --- > RFC: This is somewhat similar to eVMCS breakage and it is likely possible > to fix this in KVM. I decided to try QEMU first as this is a single > control and unlike eVMCS we don't need to keep a list of things to disable. I think you should disable "virtual-interrupt delivery" instead (which in turn requires "process posted interrupts" to be zero). That is the one that is incompatible with AutoEOI interrupts. The ugly part about fixing this in QEMU is that in theory it would be still possible to emulate virtual interrupt delivery and posted interrupts, because they operate on a completely disjoint APIC configuration than the host's. I'm not sure we want to go there though, so I'm thinking that again a KVM implementation is better. It acknowledges that this is just a limitation (workaround for a bug) in KVM. Paolo