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([2001:b07:6468:f312:29ed:810e:962c:aa0d]) by smtp.gmail.com with ESMTPSA id f11sm1369605wrm.13.2020.06.10.14.07.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 10 Jun 2020 14:07:01 -0700 (PDT) Subject: Re: [PATCH v2 08/10] KVM: x86: Switch KVM guest to using interrupts for page ready APF delivery To: Vivek Goyal , Vitaly Kuznetsov Cc: kvm@vger.kernel.org, x86@kernel.org, Andy Lutomirski , Thomas Gleixner , Borislav Petkov , "H. Peter Anvin" , Wanpeng Li , Sean Christopherson , Jim Mattson , Gavin Shan , Peter Zijlstra , linux-kernel@vger.kernel.org References: <20200525144125.143875-1-vkuznets@redhat.com> <20200525144125.143875-9-vkuznets@redhat.com> <20200610205145.GC243520@redhat.com> From: Paolo Bonzini Message-ID: Date: Wed, 10 Jun 2020 23:06:58 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200610205145.GC243520@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/06/20 22:51, Vivek Goyal wrote: >> KVM now supports using interrupt for 'page ready' APF event delivery and >> legacy mechanism was deprecated. Switch KVM guests to the new one. > Hi Vitaly, > > I see we have all this code in guest which tries to take care of > cases where PAGE_READY can be delivered before PAGE_NOT_PRESENT. In > this new schedume of things, can it still happen. We are using > an exception to deliver PAGE_NOT_PRESENT while using interrupt to > deliver PAGE_READY. > > If re-ordeing is not possible, then it will be good to get rid of > that extra complexity in guest. It is perhaps less likely but still possible, because the interrupt might be delivered to another CPU and race against the exception. Paolo