linux-kernel - Re: [PATCH] arm64/sme: Optimise SME exit on syscall entry

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Message-Id: <167354575614.3644139.13835865624687417471.b4-ty@arm.com>
Date:   Thu, 12 Jan 2023 17:49:34 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Will Deacon <will@...nel.org>, Mark Brown <broonie@...nel.org>
Cc:     Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64/sme: Optimise SME exit on syscall entry

On Tue, 10 Jan 2023 19:34:36 +0000, Mark Brown wrote:
> Our ABI says that we exit streaming mode on syscall entry. Currently we
> check if we are in streaming mode before doing this but since we have a
> SMSTOP SM instruction which will clear SVCR.SM in a single atomic operation
> we can save ourselves the read of the system register and check of the flag
> and just unconditionally do the SMSTOP SM. If we are not in streaming mode
> it results in a noop change to SVCR, if we are in streaming mode we will
> exit as desired.
> 
> [...]

Applied to arm64 (for-next/sme), thanks!

[1/1] arm64/sme: Optimise SME exit on syscall entry
      https://git.kernel.org/arm64/c/b2482807fbd4

-- 
Catalin