From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 476344570C4 for ; Tue, 4 Aug 2026 17:20:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785864062; cv=none; b=stZhENMco0lPWnOLarEg0K4r+wdd8Ug88CwgOKN+vslASjrpXA0E2sGy/HAvRMhutRwH86b3QOp2LKITab9VklFDS7zop4zAzjLhV4/Sh6yY5467Hcbn/2U+Jc1k7wfGkV5W8ZkUy+GhDklGG/YC6/1W3vKH2NBiDTSIlKuO1q4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785864062; c=relaxed/simple; bh=sj1EHV03UQltsOhcw1G68IonRj4eOw7609iEBSE4aJs=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=QR80vpFiHhMwXmIGZEYvABkfrMsRDvv/ABdRG6kq9YG7TqJbOMF/TT9hRQUfox7C+/8nq3dOMMiDzkonxgpjMAQxCUkKCXvV14bwY0kzfx0Wp8Avm3UcUX8UQ4QVjMl9XfMl3fQE5DcUWp9hSj4zkmQwMb/YER01/cPlnvTzsuM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=YlDvrxC7; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="YlDvrxC7" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id AA7361476; Tue, 4 Aug 2026 10:20:47 -0700 (PDT) Received: from J2N7QTR9R3 (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D7BEB3F632; Tue, 4 Aug 2026 10:20:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1785864051; bh=sj1EHV03UQltsOhcw1G68IonRj4eOw7609iEBSE4aJs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=YlDvrxC7mPzWVwVWkIod7BNj7FtOE4DLXcnRAhn/zykfDwWxHtuD8uKeHPQYQCBbX Io9obX8TqjiQiSrRncLa/lg71pMCILoFqCxLIsNZigx1SN1OfPRs8ndyulo9+ZsCBW BMczIWPFzqcUjbAkNp+H24+/fVDJ/Hp7dLN8PKm0= Date: Tue, 4 Aug 2026 18:20:43 +0100 From: Mark Rutland To: Catalin Marinas Cc: Bradley Morgan , will@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [RFC] [Question] memset.S old code stuff Message-ID: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Aug 04, 2026 at 04:57:54PM +0100, Catalin Marinas wrote: > On Thu, Jul 23, 2026 at 12:17:15AM +0100, Bradley Morgan wrote: > > Hey folks, sorry for the crazy asm emails, I see that in memset.S in > > arch/arm64/lib/memset.S, the code is incredibly old code, like 2013 old > > (heh). > > > > I was wondering if I could say, adapt it from optimized-routines (same > > treatment as memcpy.S essentially. > > I think Robin attempted until he realised the use of the Q registers in > the Cortex Strings library, mentioned here: > > https://lore.kernel.org/all/cover.1571073960.git.robin.murphy@arm.com/ We also subsequently looked at moving away from Cortex-strings entirely, e.g. https://lore.kernel.org/linux-arm-kernel/20230314115030.347976-1-mark.rutland@arm.com/ ... but there were open questions on the semantics, and no clear path forwards at the time. Writing the code isn't the hard part. We need to get wider agreement on the semantics, test on a variety of platforms, etc. For now, I think it'd be best to leave as-is, since it's a time sink for reviewers. Mark.