From: Mark Brown <broonie@kernel.org>
To: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Shuah Khan <shuah@kernel.org>,
David Spickett <David.Spickett@arm.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH 1/3] arm64/fpsimd: Ensure SME storage is allocated after SVE VL changes
Date: Thu, 20 Jul 2023 13:27:10 +0100 [thread overview]
Message-ID: <3ce4fc14-bd43-47e9-aa37-59bb3cd5d051@sirena.org.uk> (raw)
In-Reply-To: <20230720105235.GD11034@willie-the-truck>
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On Thu, Jul 20, 2023 at 11:52:36AM +0100, Will Deacon wrote:
> On Thu, Jul 13, 2023 at 09:06:04PM +0100, Mark Brown wrote:
> > Since the ABI does not specify that changing the SVE vector length disturbs
> > SME state, and since SVE code may not be aware of SME code in the process,
> > we shouldn't simply discard any ZA state. Instead immediately reallocate
> > the storage for SVE if SME is active, and disable SME if we change the SVE
> > vector length while there is no SME state active.
> What is the advantage of keep the old behaviour in this case? In other
> words, if it's acceptable to reallocate the state when SME is active, why
> not just reallocate in all cases?
It was minimising the changes to the status quo given how attached
people often are to these things.
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next prev parent reply other threads:[~2023-07-20 12:27 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-13 20:06 [PATCH 0/3] arm64/fpsimd: Fix use after free in SME when changing SVE VL Mark Brown
2023-07-13 20:06 ` [PATCH 1/3] arm64/fpsimd: Ensure SME storage is allocated after SVE VL changes Mark Brown
2023-07-17 11:19 ` David Spickett
2023-07-20 10:52 ` Will Deacon
2023-07-20 12:27 ` Mark Brown [this message]
2023-07-13 20:06 ` [PATCH 2/3] kselftest/arm64: Add a test case for SVE VL changes with SME active Mark Brown
2023-07-13 20:06 ` [PATCH 3/3] kselftest/arm64: Validate that changing one VL type does not affect another Mark Brown
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