From: Marc Zyngier <maz@kernel.org>
To: Kristina Martsenko <kristina.martsenko@arm.com>
Cc: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
kvm@vger.kernel.org, James Morse <james.morse@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Oliver Upton <oliver.upton@linux.dev>,
Zenghui Yu <yuzenghui@huawei.com>,
isaku.yamahata@intel.com, seanjc@google.com, pbonzini@redhat.com,
stable@vger.kernek.org
Subject: Re: [PATCH] KVM: arm64: Disable preemption in kvm_arch_hardware_enable()
Date: Wed, 05 Jul 2023 10:36:08 +0100 [thread overview]
Message-ID: <86o7kqwvhz.wl-maz@kernel.org> (raw)
In-Reply-To: <4c92ceb6-34a2-3128-9b26-dd58e4d7612a@arm.com>
On Tue, 04 Jul 2023 19:32:09 +0100,
Kristina Martsenko <kristina.martsenko@arm.com> wrote:
>
> On 03/07/2023 17:35, Marc Zyngier wrote:
> > Since 0bf50497f03b ("KVM: Drop kvm_count_lock and instead protect
> > kvm_usage_count with kvm_lock"), hotplugging back a CPU whilst
> > a guest is running results in a number of ugly splats as most
> > of this code expects to run with preemption disabled, which isn't
> > the case anymore.
> >
> > While the context is preemptable, it isn't migratable, which should
> > be enough. But we have plenty of preemptible() checks all over
> > the place, and our per-CPU accessors also disable preemption.
> >
> > Since this affects released versions, let's do the easy fix first,
> > disabling preemption in kvm_arch_hardware_enable(). We can always
> > revisit this with a more invasive fix in the future.
> >
> > Fixes: 0bf50497f03b ("KVM: Drop kvm_count_lock and instead protect kvm_usage_count with kvm_lock")
> > Reported-by: Kristina Martsenko <kristina.martsenko@arm.com>
> > Tested-by: Kristina Martsenko <kristina.martsenko@arm.com>
> > Signed-off-by: Marc Zyngier <maz@kernel.org>
> > Link: https://lore.kernel.org/r/aeab7562-2d39-e78e-93b1-4711f8cc3fa5@arm.com
> > Cc: stable@vger.kernek.org # v6.3, v6.4
>
> Typo here, didn't make it to the stable list (kernek.org -> kernel.org)
Yeah, I had a bad day (I also typoed Catalin's address in a separate
email...).
M.
--
Without deviation from the norm, progress is not possible.
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next prev parent reply other threads:[~2023-07-05 9:36 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-03 16:35 [PATCH] KVM: arm64: Disable preemption in kvm_arch_hardware_enable() Marc Zyngier
2023-07-04 18:32 ` Kristina Martsenko
2023-07-04 18:54 ` Oliver Upton
2023-07-05 9:36 ` Marc Zyngier [this message]
2023-07-10 18:04 ` Sean Christopherson
2023-07-10 18:16 ` Marc Zyngier
2023-07-10 18:20 ` Oliver Upton
2023-07-10 22:13 ` Sean Christopherson
2023-07-11 20:00 ` Oliver Upton
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