From: Marc Zyngier <maz@kernel.org>
To: Oliver Upton <oliver.upton@linux.dev>
Cc: kvmarm@lists.linux.dev, Joey Gouly <joey.gouly@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Zenghui Yu <yuzenghui@huawei.com>
Subject: Re: [PATCH 0/5] KVM: arm64: vgic-v3: Fix yet another lock ordering turd
Date: Fri, 05 Sep 2025 09:29:43 +0100 [thread overview]
Message-ID: <87o6rpz4i0.wl-maz@kernel.org> (raw)
In-Reply-To: <20250904062348.223976-1-oliver.upton@linux.dev>
On Thu, 04 Sep 2025 07:23:43 +0100,
Oliver Upton <oliver.upton@linux.dev> wrote:
>
> syzkaller found yet another locking bug in the VGIC [*], this time due
> to nesting a 'plain' spinlock (xa_lock) inside of a raw spinlock
> (ap_list_lock). Given the way we do refcounts on LPIs it is possible
> for this exact sort of issue to crop up where the last reference may
> be dropped in unexpected places.
>
> Small series to fix the issue by deferring xarray modifications outside
> of the ap_list_lock critical section along with some slight lockdep
> hinting to make these rare bugs a bit more obvious.
I quite like that we get a release operation, rather than the slightly
counter-intuitive construct we have today.
With the couple of issues that Ben and I raised fixed:
Reviewed-by: Marc Zyngier <maz@kernel.org>
M.
--
Jazz isn't dead. It just smells funny.
prev parent reply other threads:[~2025-09-05 8:29 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-04 6:23 [PATCH 0/5] KVM: arm64: vgic-v3: Fix yet another lock ordering turd Oliver Upton
2025-09-04 6:23 ` [PATCH 1/5] KVM: arm64: vgic-v3: Use bare refcount for VGIC LPIs Oliver Upton
2025-09-04 6:23 ` [PATCH 2/5] KVM: arm64: Spin off release helper from vgic_put_irq() Oliver Upton
2025-09-04 6:23 ` [PATCH 3/5] KVM: arm64: vgic-v3: Erase LPIs from xarray outside of raw spinlocks Oliver Upton
2025-09-05 7:44 ` Marc Zyngier
2025-09-05 7:19 ` Oliver Upton
2025-09-04 6:23 ` [PATCH 4/5] KVM: arm64: vgic-v3: Don't require IRQs be disabled for LPI xarray lock Oliver Upton
2025-09-05 8:13 ` Marc Zyngier
2025-09-05 8:55 ` Oliver Upton
2025-09-04 6:23 ` [PATCH 5/5] KVM: arm64: vgic-v3: Indicate vgic_put_irq() may take " Oliver Upton
2025-09-04 10:25 ` Ben Horgan
2025-09-04 8:19 ` Oliver Upton
2025-09-05 8:29 ` Marc Zyngier [this message]
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