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[91.219.240.2]) by smtp.gmail.com with ESMTPSA id f6sm3504275wme.32.2020.09.09.01.49.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Sep 2020 01:49:28 -0700 (PDT) From: Vitaly Kuznetsov To: Ingo Molnar 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 In-Reply-To: <20200909081613.GB2446260@gmail.com> References: <20200908135350.355053-1-vkuznets@redhat.com> <20200908135350.355053-3-vkuznets@redhat.com> <20200909081613.GB2446260@gmail.com> Date: Wed, 09 Sep 2020 10:49:27 +0200 Message-ID: <878sdjmj1k.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Ingo Molnar writes: > * 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> My wild guess would be that kvmtool doesn't manually set any of the KVM PV features: [vitty@vitty kvmtool]$ git grep KVM_FEATURE_ [vitty@vitty kvmtool]$ it just blindly passes whatever it gets from KVM via KVM_GET_SUPPORTED_CPUID to KVM_SET_CPUID2 and KVM_FEATURE_ASYNC_PF_INT among other PV features is set there by default. > > 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! -- Vitaly