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[84.0.120.1]) by smtp.gmail.com with ESMTPSA id c4sm3013426wrp.85.2020.09.09.01.16.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Sep 2020 01:16:15 -0700 (PDT) Date: Wed, 9 Sep 2020 10:16:13 +0200 From: Ingo Molnar To: Vitaly Kuznetsov Cc: kvm@vger.kernel.org, x86@kernel.org, Paolo Bonzini , Sean Christopherson , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Andy Lutomirski Subject: Re: [PATCH 2/2] x86/kvm: don't forget to ACK async PF IRQ Message-ID: <20200909081613.GB2446260@gmail.com> References: <20200908135350.355053-1-vkuznets@redhat.com> <20200908135350.355053-3-vkuznets@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200908135350.355053-3-vkuznets@redhat.com> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org * Vitaly Kuznetsov wrote: > Merge commit 26d05b368a5c0 ("Merge branch 'kvm-async-pf-int' into HEAD") > tried to adapt the new interrupt based async PF mechanism to the newly > introduced IDTENTRY magic but unfortunately it missed the fact that > DEFINE_IDTENTRY_SYSVEC() doesn't call ack_APIC_irq() on its own and > all DEFINE_IDTENTRY_SYSVEC() users have to call it manually. > > As the result all multi-CPU KVM guest hang on boot when > KVM_FEATURE_ASYNC_PF_INT is present. The breakage went unnoticed because no > KVM userspace (e.g. QEMU) currently set it (and thus async PF mechanism > is currently disabled) but we're about to change that. > > Fixes: 26d05b368a5c0 ("Merge branch 'kvm-async-pf-int' into HEAD") > Signed-off-by: Vitaly Kuznetsov This also fixes a kvmtool regression, but interestingly it does not set KVM_FEATURE_ASYNC_PF_INT either AFAICS: kepler:~/kvmtool.git> git grep KVM_FEATURE_ASYNC_PF_INT kepler:~/kvmtool.git> kepler:~/kvmtool.git> grep url .git/config url = https://git.kernel.org/pub/scm/linux/kernel/git/will/kvmtool.git So either I missed the flag-setting in the kvmtools.git source, or maybe there's some other way to trigger this bug? Anyway, please handle this as a v5.9 regression: Tested-by: Ingo Molnar Thanks, Ingo