From: Oliver Upton <oliver.upton@linux.dev>
To: kvmarm@lists.linux.dev, Will Deacon <will@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>,
linux-arm-kernel@lists.infradead.org,
Sebastian Ene <sebastianene@google.com>,
Sudeep Holla <sudeep.holla@arm.com>,
Quentin Perret <qperret@google.com>,
Marc Zyngier <maz@kernel.org>
Subject: Re: [PATCH] KVM: arm64: Use acquire/release to communicate FF-A version negotiation
Date: Mon, 7 Apr 2025 15:07:46 -0700 [thread overview]
Message-ID: <174406364625.3332785.16419054127617723958.b4-ty@linux.dev> (raw)
In-Reply-To: <20250407152755.1041-1-will@kernel.org>
On Mon, 07 Apr 2025 16:27:55 +0100, Will Deacon wrote:
> The pKVM FF-A proxy rejects FF-A requests other than FFA_VERSION until
> version negotiation is complete, which is signalled by setting the
> global 'has_version_negotiated' variable.
>
> To avoid excessive locking, this variable is checked directly from
> kvm_host_ffa_handler() in response to an FF-A call, but this can race
> against another CPU performing the negotiation and potentially lead to
> reading a torn value (incredibly unlikely for a 'bool') or problematic
> re-ordering of the accesses to 'has_version_negotiated' and
> 'hyp_ffa_version' whereby a stale version number could be read by
> __do_ffa_mem_xfer().
>
> [...]
Applied to fixes, thanks!
[1/1] KVM: arm64: Use acquire/release to communicate FF-A version negotiation
https://git.kernel.org/kvmarm/kvmarm/c/a344e258acb0
--
Best,
Oliver
prev parent reply other threads:[~2025-04-07 22:07 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-04-07 15:27 [PATCH] KVM: arm64: Use acquire/release to communicate FF-A version negotiation Will Deacon
2025-04-07 22:07 ` Oliver Upton [this message]
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