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([2001:b07:6468:f312:bd61:914:5c2f:2580]) by smtp.gmail.com with ESMTPSA id w66sm3973000wma.38.2020.04.07.15.07.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 07 Apr 2020 15:07:24 -0700 (PDT) Subject: Re: [PATCH v2] x86/kvm: Disable KVM_ASYNC_PF_SEND_ALWAYS To: Andy Lutomirski , Thomas Gleixner Cc: Vivek Goyal , Peter Zijlstra , Andy Lutomirski , LKML , X86 ML , kvm list , stable References: <87eeszjbe6.fsf@nanos.tec.linutronix.de> From: Paolo Bonzini Message-ID: <2776fced-54c2-40eb-7921-1c68236c7f70@redhat.com> Date: Wed, 8 Apr 2020 00:07:22 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/04/20 23:41, Andy Lutomirski wrote: > 2. Access to bad memory results in #MC. Sure, #MC is a turd, but > it’s an *architectural* turd. By all means, have a nice simple PV > mechanism to tell the #MC code exactly what went wrong, but keep the > overall flow the same as in the native case. > > I think I like #2 much better. It has another nice effect: a good > implementation will serve as a way to exercise the #MC code without > needing to muck with EINJ or with whatever magic Tony uses. The > average kernel developer does not have access to a box with testable > memory failure reporting. I prefer #VE, but I can see how #MC has some appeal. However, #VE has a mechanism to avoid reentrancy, unlike #MC. How would that be better than the current mess with an NMI happening in the first few instructions of the #PF handler? Paolo