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([2001:b07:6468:f312:ac19:d1fb:3f5f:d54f]) by smtp.gmail.com with ESMTPSA id g74sm11257055wme.44.2020.04.29.23.49.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 29 Apr 2020 23:49:41 -0700 (PDT) Subject: Re: [PATCH RFC 4/6] KVM: x86: acknowledgment mechanism for async pf page ready notifications To: Vitaly Kuznetsov , x86@kernel.org, kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Sean Christopherson , Wanpeng Li , Jim Mattson References: <20200429093634.1514902-1-vkuznets@redhat.com> <20200429093634.1514902-5-vkuznets@redhat.com> From: Paolo Bonzini Message-ID: Date: Thu, 30 Apr 2020 08:49:41 +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: <20200429093634.1514902-5-vkuznets@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 29/04/20 11:36, Vitaly Kuznetsov wrote: > + case MSR_KVM_ASYNC_PF_ACK: > + if (data & 0x1) > + kvm_check_async_pf_completion(vcpu); > + break; Does this work if interrupts are turned off? I think in that case kvm_check_async_pf_completion will refuse to make progress. You need to make this bit stateful (e.g. 1 = async PF in progress, 0 = not in progress), and check that for page ready notifications instead of EFLAGS.IF. This probably means that; - it might be simpler to move it to the vector MSR - it's definitely much simpler to remove the #PF-based mechanism for injecting page ready notifications. Thanks, Paolo