linux-kernel - Re: [PATCH 0/5] arm64/sme: Support disabling streaming mode via ptrace on SME only systems

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Message-Id: <175819643529.3451422.10117622348778381735.b4-ty@kernel.org>
Date: Thu, 18 Sep 2025 17:43:06 +0100
From: Will Deacon <will@...nel.org>
To: Catalin Marinas <catalin.marinas@....com>,
	Shuah Khan <shuah@...nel.org>,
	Jonathan Corbet <corbet@....net>,
	Oleg Nesterov <oleg@...hat.com>,
	Mark Brown <broonie@...nel.org>
Cc: kernel-team@...roid.com,
	Will Deacon <will@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	David Spickett <david.spickett@....com>,
	Thiago Jung Bauermann <thiago.bauermann@...aro.org>,
	Luis Machado <luis.machado.foss@...il.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-kselftest@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org
Subject: Re: [PATCH 0/5] arm64/sme: Support disabling streaming mode via ptrace on SME only systems

On Wed, 20 Aug 2025 19:29:02 +0100, Mark Brown wrote:
> Currently it is not possible to disable streaming mode via ptrace on SME
> only systems, the interface for doing this is to write via NT_ARM_SVE but
> such writes will be rejected on a system without SVE support. Enable this
> functionality by allowing userspace to write SVE_PT_REGS_FPSIMD format data
> via NT_ARM_SVE with the vector length set to 0 on SME only systems. Such
> writes currently error since we require that a vector length is specified
> which should minimise the risk that existing software is relying on current
> behaviour.
> 
> [...]

Applied first two selftests to arm64 (for-next/selftests), thanks!

[1/5] kselftest/arm64: Verify that we reject out of bounds VLs in sve-ptrace
      https://git.kernel.org/arm64/c/dd68f51febbd
[2/5] kselftest/arm64: Check that unsupported regsets fail in sve-ptrace
      https://git.kernel.org/arm64/c/09b5febf8426

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev