From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 942BFC433EF for ; Thu, 7 Apr 2022 11:07:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=nsSA//49KdHqaVR6UX5wakzZanQSY++uV6FDkBC5MD8=; b=y5d9z0OOt4Ltv7 +lMkyjMN1O/SpkzrSlrhX/bMxfuc/06it9y1BvjfYiOBQMBUJmrrdxOSq73bgWLQrzATB4IVsJq+q LkMqiJp+BvM6iQ7Qry/0+jMO8Cuor8oZUapo+H0m+sRfNEtsIRs+4HCFGuCNIlJiIlILSQtodKYXm ftGZgU+a8fQAhfSQK6MnhhhJjJf6kmUC1KqHj6yD4NJ7kSwXUoVGaLhQRxRnowf7Bku09QYJHMN9U mMfxQ397C1ZOs3iRtTTzIAWmmXlkcNJV2YrSWLNiMtYgBqm+58yz6zgQzyfX+3Qe3v+lHJ424HvZe fabVhsGv8EUTuquxYfrg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1ncPy3-00BT79-Sj; Thu, 07 Apr 2022 11:06:24 +0000 Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1ncPxy-00BT5V-2i for linux-arm-kernel@lists.infradead.org; Thu, 07 Apr 2022 11:06:19 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id E463A61E24; Thu, 7 Apr 2022 11:06:16 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B8100C385A0; Thu, 7 Apr 2022 11:06:13 +0000 (UTC) Date: Thu, 7 Apr 2022 12:06:10 +0100 From: Catalin Marinas To: Muchun Song Cc: Will Deacon , Marc Zyngier , Arnd Bergmann , Greg Kroah-Hartman , Andrew Morton , Linus Torvalds , Linux Memory Management List , LAK , LKML , Herbert Xu , "David S. Miller" Subject: Re: [PATCH 07/10] crypto: Use ARCH_DMA_MINALIGN instead of ARCH_KMALLOC_MINALIGN Message-ID: References: <20220405135758.774016-1-catalin.marinas@arm.com> <20220405135758.774016-8-catalin.marinas@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220407_040618_266109_E37B397A X-CRM114-Status: GOOD ( 34.84 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Apr 07, 2022 at 06:00:10PM +0800, Muchun Song wrote: > On Thu, Apr 7, 2022 at 5:25 PM Catalin Marinas wrote: > > On Thu, Apr 07, 2022 at 02:14:15PM +0800, Muchun Song wrote: > > > On Tue, Apr 05, 2022 at 02:57:55PM +0100, Catalin Marinas wrote: > > > > ARCH_DMA_MINALIGN represents the minimum (static) alignment for safe DMA > > > > operations while ARCH_KMALLOC_MINALIGN is the minimum kmalloc() objects > > > > alignment. > > > > > > > > Signed-off-by: Catalin Marinas > > > > Cc: Herbert Xu > > > > Cc: "David S. Miller" > > > > --- > > > > include/linux/crypto.h | 2 +- > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > diff --git a/include/linux/crypto.h b/include/linux/crypto.h > > > > index 2324ab6f1846..654b9c355575 100644 > > > > --- a/include/linux/crypto.h > > > > +++ b/include/linux/crypto.h > > > > @@ -167,7 +167,7 @@ > > > > * maintenance for non-coherent DMA (cache invalidation in particular) does not > > > > * affect data that may be accessed by the CPU concurrently. > > > > */ > > > > -#define CRYPTO_MINALIGN ARCH_KMALLOC_MINALIGN > > > > +#define CRYPTO_MINALIGN ARCH_DMA_MINALIGN > > > > > > I don't think this should be changed since ARCH_KMALLOC_MINALIGN is > > > already aligned with the size what you need. > > > > With this series, ARCH_KMALLOC_MINALIGN is no longer safe for > > non-coherent DMA on all arm64 SoCs, that's what ARCH_DMA_MINALIGN will > > cover. > > > > Now, looking at the comment for CRYPTO_MINALIGN, one aspect it covers is > > the minimum alignment required by C for the crypto_tfm structure access. > > So a smaller ARCH_KMALLOC_MINALIGN would do. But the other part of the > > comment mentions in-structure alignment for non-coherent DMA. Here we'd > > need the upper bound alignment, ARCH_DMA_MINALIGN. > > > > I'll follow up on Herbert's email as I think he has a good point on > > structure vs kmalloc() alignment. > > Got it. Now I know what you want to do. You want to set > ARCH_KMALLOC_MINALIGN to 64, however, the smallest > size of kmem_cache depends on the cache line size at > runtime. But we have to know the safe alignment at building > time. So we have to make those align with ARCH_DMA_MINALIGN. > Right? Right. > I think you are on the right road since most CPUs have a 64-byte cache > line. Yeah, apart from about three SoCs with 128, the rest use 64-byte cache lines. Longer term we should try reduce such alignment below the cache line size *if* the SoC fully DMA-coherent (like x86). In that case cache maintenance for DMA doesn't exist, so there's no risk to smaller allocations. Of course, one can use a kmem_cache_create() with SLAB_HWCACHE_ALIGN and get the cacheline alignment for performance reasons. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel