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 3371A3750CF; Fri, 19 Jun 2026 13:04:54 +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=1781874295; cv=none; b=EOzfKVenTwL7SDxRTN0Yll/h4D9Z0uIaa1gx65jxvsCuOPkTvsLhCbvatKwUZcHb0d4AxzcXNoGRom0y6aRByx9YW6po6PZKVH0yjAll97KyejXNK2KTnzNOND+KWqVe+rdfPZ4ZLhlrEYVQqJ6XRZAMmkQWlfQA6we2p3orv9A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781874295; c=relaxed/simple; bh=e9pfEYbv59UVNvg5pd3j1Yh0i55qXWOlAw6aQXf2fiI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=kYatG47jNTsPTcVTYsX36GGXGNaJZCbXk1HQWu8ZBJMJtTaUI/IW2nlFlIWwVn6r93LeKK0zCOYKUSF6YCi3nJxryMU8uZ5mShojJS1MTLoNO6oxh7S0Iq5VoaCV5hYnbdYZIgEEYQOtz7GjzYVEkY1Rgj/ZuRgMfEmGTYf2EyI= 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=lQUOPpbA; 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="lQUOPpbA" 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 E85D24A92; Fri, 19 Jun 2026 06:04:48 -0700 (PDT) Received: from arm.com (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6E4AD3F763; Fri, 19 Jun 2026 06:04:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1781874293; bh=e9pfEYbv59UVNvg5pd3j1Yh0i55qXWOlAw6aQXf2fiI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=lQUOPpbAmN6Zr1EYJgextc9Lnki8Ehn68EA514fFROJG93hMv4r2Cfa/r8NEkWg3n w7/Zq2/WnP0TUUTs/hsA6wrxV4sm6R2stNIFSF+9iXhA2oqOiIZLzOIr6XQovIdoEu /E9iWQPaERn1E4Z9+FmbsevKh/DyS57CcpVOvJzY= Date: Fri, 19 Jun 2026 14:04:47 +0100 From: Catalin Marinas To: Harry Yoo Cc: Dev Jain , ryabinin.a.a@gmail.com, akpm@linux-foundation.org, corbet@lwn.net, glider@google.com, andreyknvl@gmail.com, dvyukov@google.com, vincenzo.frascino@arm.com, kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, skhan@linuxfoundation.org, workflows@vger.kernel.org, linux-doc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, ryan.roberts@arm.com, anshuman.khandual@arm.com, kaleshsingh@google.com, 21cnbao@gmail.com, david@kernel.org, will@kernel.org Subject: Re: [RFC PATCH 0/2] kasan: hw_tags: Add option to tag only at allocation time Message-ID: References: <20260612044425.763060-1-dev.jain@arm.com> <2a7d21fa-28c1-446c-97f5-2513f29157d3@kernel.org> Precedence: bulk X-Mailing-List: workflows@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: <2a7d21fa-28c1-446c-97f5-2513f29157d3@kernel.org> On Thu, Jun 18, 2026 at 11:05:43PM +0900, Harry Yoo wrote: > On 6/18/26 10:35 PM, Harry Yoo wrote: > > On 6/12/26 1:44 PM, Dev Jain wrote: > >> Introduce a boot option to tag only at allocation time of the objects. This > >> reduces KASAN MTE overhead, the tradeoff being reduced ability of > >> catching bugs. > > > > I think most of overhead when enabling MTE comes from loading and > > validing tags for every memory access (either in SYNC or ASYNC mode), > > rather than from storing tags. > > Is there any reason not to use STGM instead of STG + DC GVA when > setting/clearing tags for large sizes when we know they are properly > aligned? STGM is intended for copying tags when paired with LDGM. Have you seen hardware where STGM is faster than STG or DC GVA? For properly aligned buffers, I'd expect DC GVA to behave at least on par with STGM. -- Catalin