From: Ingo Molnar <mingo@kernel.org>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: kvm@vger.kernel.org, x86@kernel.org,
Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Andy Lutomirski <luto@kernel.org>
Subject: Re: [PATCH 2/2] x86/kvm: don't forget to ACK async PF IRQ
Date: Wed, 9 Sep 2020 10:16:13 +0200 [thread overview]
Message-ID: <20200909081613.GB2446260@gmail.com> (raw)
In-Reply-To: <20200908135350.355053-3-vkuznets@redhat.com>
* Vitaly Kuznetsov <vkuznets@redhat.com> 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 <vkuznets@redhat.com>
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 <mingo@kernel.org>
Thanks,
Ingo
next prev parent reply other threads:[~2020-09-09 8:16 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-08 13:53 [PATCH 0/2] x86/kvm: fix interrupts based APF mechanism Vitaly Kuznetsov
2020-09-08 13:53 ` [PATCH 1/2] x86/kvm: properly use DEFINE_IDTENTRY_SYSVEC() macro Vitaly Kuznetsov
2020-09-08 13:53 ` [PATCH 2/2] x86/kvm: don't forget to ACK async PF IRQ Vitaly Kuznetsov
2020-09-09 8:16 ` Ingo Molnar [this message]
2020-09-09 8:49 ` Vitaly Kuznetsov
2020-09-12 6:22 ` Paolo Bonzini
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