From: Oliver Upton <oliver.upton@linux.dev>
To: Kristina Martsenko <kristina.martsenko@arm.com>
Cc: Marc Zyngier <maz@kernel.org>,
isaku.yamahata@intel.com, seanjc@google.com, pbonzini@redhat.com,
kvmarm@lists.linux.dev, kvm@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
James Morse <james.morse@arm.com>
Subject: Re: KVM CPU hotplug notifier triggers BUG_ON on arm64
Date: Sat, 1 Jul 2023 10:42:28 -0700 [thread overview]
Message-ID: <ZKBlhJwl9YD5FHvs@linux.dev> (raw)
In-Reply-To: <aeab7562-2d39-e78e-93b1-4711f8cc3fa5@arm.com>
Hi Kristina,
Thanks for the bug report.
On Sat, Jul 01, 2023 at 01:50:52PM +0100, Kristina Martsenko wrote:
> Hi,
>
> When I try to online a CPU on arm64 while a KVM guest is running, I hit a
> BUG_ON(preemptible()) (as well as a WARN_ON). See below for the full log.
>
> This is on kvmarm/next, but seems to have been broken since 6.3. Bisecting it
> points at commit:
>
> 0bf50497f03b ("KVM: Drop kvm_count_lock and instead protect kvm_usage_count with kvm_lock")
Makes sense. We were using a spinlock before, which implictly disables
preemption.
Well, one way to hack around the problem would be to just cram
preempt_{disable,enable}() into kvm_arch_hardware_disable(), but that's
kinda gross in the context of cpuhp which isn't migratable in the first
place. Let me have a look...
--
Thanks,
Oliver
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next prev parent reply other threads:[~2023-07-01 17:43 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-01 12:50 KVM CPU hotplug notifier triggers BUG_ON on arm64 Kristina Martsenko
2023-07-01 17:42 ` Oliver Upton [this message]
2023-07-03 9:45 ` Marc Zyngier
2023-07-03 10:36 ` Kristina Martsenko
2023-07-03 16:02 ` Oliver Upton
2023-07-03 16:38 ` Marc Zyngier
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