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([2001:b07:6468:f312:ac19:d1fb:3f5f:d54f]) by smtp.gmail.com with ESMTPSA id v7sm7016551wmg.3.2020.04.29.03.53.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 29 Apr 2020 03:53:34 -0700 (PDT) Subject: Re: [PATCH RFC 6/6] KVM: x86: Switch KVM guest to using interrupts for page ready APF delivery 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> <20200429093634.1514902-7-vkuznets@redhat.com> From: Paolo Bonzini Message-ID: Date: Wed, 29 Apr 2020 12:53:33 +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: <20200429093634.1514902-7-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: > + > + if (__this_cpu_read(apf_reason.enabled)) { > + reason = __this_cpu_read(apf_reason.reason); > + if (reason == KVM_PV_REASON_PAGE_READY) { > + token = __this_cpu_read(apf_reason.token); > + /* > + * Make sure we read 'token' before we reset > + * 'reason' or it can get lost. > + */ > + mb(); > + __this_cpu_write(apf_reason.reason, 0); > + kvm_async_pf_task_wake(token); > + } If tokens cannot be zero, could we avoid using reason for the page ready interrupt (and ultimately retire "reason" completely)? Paolo