From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D852D265CA2; Mon, 6 Jul 2026 13:49:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783345768; cv=none; b=JWZ6jDUn5CaviarrhEDM2pn8mouGOAlFLLsUEH+Bnn0qPmpfJmzzBzq/1ti/VCJlpHsvoI1a9sQlaDu9egj1ftIRXmrdVCkzi/2BODd9jzJ1MAQZm+Ppl52ML6edzGd9BIevuyFc8TthLyUfdD3cTuKOPnwE8GWtZFdZKScPvmc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783345768; c=relaxed/simple; bh=wZOvNFkBPsWuGeuJiDW57s7pVPfH0Iv5i4aVAjcdTGI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=bEF1I/S8Q1EiJjAJUVXssSUMMTPE1GaNGr0KiFMCS5orKk9jXDJnOB6/duCYwJKRioTT7hZoAShqpBpfzs7uepTwDD9qHmIq2SOT88ULheTNc6Oh/AZ1MN05bn7/Hw7wCHOasQywewatwaEN3IABLtVg83k8DitIYbg1heP03Oc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=cfweDhmY; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="cfweDhmY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9DD4A1F000E9; Mon, 6 Jul 2026 13:49:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783345767; bh=wK0aCBXBbwqdK294JK8uznzPRp3oLmGuOxio1ftZy3s=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=cfweDhmY3uzvwT/ivKj11445D9BHzpepvwDhcWWBY0Ax9ECQOnkIy2JdCFBTcQh+O OL5bc+sjjh6g1WZpz3gftwLq3vURxlcGhKoQlk3w1QcGdY5BCWKL3qNxOepmz9mnHw hLf8zsYFvcrlxKTU2kIii7Q9VvyYogkTc9t2AndndPnTcQ+2jYibLpoixg1z4E2qHw 3ZKVmPO5NGQEfdRfmdvnPu4KES5JWkbJaMtwRLpstX//I7D3xenCII9qgmhmfLP9zx zh226Qdu3vaRu6SDP2qO8V1dLSuWZZGFYZ3k5Es3tJa5Lf3fTt4n+n4Z/Z+Ijpxi/J QSIKNgtpyQ+zA== Message-ID: Date: Mon, 6 Jul 2026 15:49:21 +0200 Precedence: bulk X-Mailing-List: linux-arch@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 6/8] string: introduce memcpy_nt() helpers To: Li Zhe Cc: akpm@linux-foundation.org, apopple@nvidia.com, arnd@arndb.de, bp@alien8.de, dave.hansen@linux.intel.com, kees@kernel.org, linux-arch@vger.kernel.org, linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mingo@redhat.com, rppt@kernel.org, tglx@kernel.org, x86@kernel.org References: <20260706115313.50524-1-lizhe.67@bytedance.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/6/26 13:53, Li Zhe wrote: > On Mon, Jul 6, 2026 at 11:18:48AM +0200, david@kernel.org wrote: > >>> + >>> +#define __HAVE_ARCH_MEMCPY_NT 1 >>> +/* >>> + * Reuse the existing x86 flushcache backend as the nt copy primitive. >>> + * Callers pair it with memcpy_nt_drain() when later stores must be >>> + * ordered after the copy. >>> + */ >>> +static __always_inline void memcpy_nt(void *dst, const void *src, size_t cnt) >>> +{ >>> + memcpy_flushcache(dst, src, cnt); >>> +} >> >> In particular if you end up with a single function (that jsut requires a write >> memory barrier afterwards), please make this >> >> #define memcpy_nt memcpy_nt >> >> instead. > > Thanks for the review. > > Just to make sure I understood this correctly: do you mean that, rather > than using a separate __HAVE_ARCH_MEMCPY_NT feature macro, you would > prefer the usual self-macro override pattern, with > > #define memcpy_nt memcpy_nt > > in arch/x86/include/asm/string_64.h and the generic fallback kept under > #ifndef memcpy_nt in include/linux/string.h? Yes, that's what Linus suggested as the preferred way for single functions when it came up in different context recently. -- Cheers, David