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([2001:b07:6468:f312:5e2c:eb9a:a8b6:fd3e]) by smtp.gmail.com with ESMTPSA id v7sm8380791edd.4.2021.07.06.16.41.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 06 Jul 2021 16:41:14 -0700 (PDT) Subject: Re: exception vs SIGALRM race (was: Re: guest/host mem out of sync on core2duo?) To: stsp , Jim Mattson Cc: Sean Christopherson , kvm@vger.kernel.org, David Woodhouse , "ntsironis@arrikto.com" References: <73f1f90e-f952-45a4-184e-1aafb3e4a8fd@yandex.ru> <23b00d8a-1732-0b0b-cd8d-e802f7aca87c@yandex.ru> <1501d6d3-4dab-3eca-1d82-1e1954e293e1@redhat.com> From: Paolo Bonzini Message-ID: <54270fb7-91ac-f10d-5879-956f42372536@redhat.com> Date: Wed, 7 Jul 2021 01:41:13 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 07/07/21 00:22, stsp wrote: > I confirm that this works, thanks. > Sadly the problematic patch was > CCed to -stable, and is now present > in all kernels, like ubuntu's 5.8.0-55-generic. > Since AFAICT it didn't contain the > important/security fix, I think it > shouldn't have been CCed to -stable. > > Can we revert it from -stable? > That will mean a relatively quick > fix for most of current users. It was a bugfix, see the commit message: when userspace requests an IRQ window vmexit, an interrupt in the local APIC can cause kvm_cpu_has_interrupt() to be true and thus kvm_vcpu_ready_for_interrupt_injection() to return false. When this happens, vcpu_run does not exit to userspace but the interrupt window vmexits keep occurring. The VM loops without any hope of making progress. Thanks for the testing! Paolo