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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7CBB2C4332F for ; Tue, 12 Apr 2022 10:55:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239212AbiDLK5Y (ORCPT ); Tue, 12 Apr 2022 06:57:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53746 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1356630AbiDLKpc (ORCPT ); Tue, 12 Apr 2022 06:45:32 -0400 Received: from fornost.hmeau.com (helcar.hmeau.com [216.24.177.18]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5812684EE4 for ; Tue, 12 Apr 2022 02:41:24 -0700 (PDT) Received: from gwarestrin.arnor.me.apana.org.au ([192.168.103.7]) by fornost.hmeau.com with smtp (Exim 4.94.2 #2 (Debian)) id 1neD17-001sqd-Uh; Tue, 12 Apr 2022 19:40:59 +1000 Received: by gwarestrin.arnor.me.apana.org.au (sSMTP sendmail emulation); Tue, 12 Apr 2022 17:40:58 +0800 Date: Tue, 12 Apr 2022 17:40:58 +0800 From: Herbert Xu To: Catalin Marinas Cc: Ard Biesheuvel , Will Deacon , Marc Zyngier , Arnd Bergmann , Greg Kroah-Hartman , Andrew Morton , Linus Torvalds , linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, "David S. Miller" Subject: Re: [PATCH 07/10] crypto: Use ARCH_DMA_MINALIGN instead of ARCH_KMALLOC_MINALIGN Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 12, 2022 at 10:32:58AM +0100, Catalin Marinas wrote: > > At a quick grep, most cra_alignmask values are currently 15 or smaller. > I'm not convinced the driver needs to know about the CPU cache > alignment. We could set cra_alignmask to CRYPTO_MINALIGN but that would > incur unnecessary overhead via function like setkey_unaligned() when the > arch_kmalloc_minalign() was already sufficient for DMA safety. > > Maybe I miss some use-cases or I focus too much on DMA safety. The alignment was never designed for DMA. It's mainly for CPUs that provide accelerated instructions that require a certain amount of alignment, most commonly 16 bytes. Therefore CRYPTO_MINALIGN was never meant to be a guarantee for DMA alignment. Any drivers relying on this is simply broken. I understand that on ARM for historical reasons you have had a situation that CRYPTO_MINALIGN happened to be large enough to guarantee DMA alignment. I totally agree with your patch to try to fix this but it should not penalise other architectures and raise the CRYPTO_MINALIGN unnecessarily. I think if CRYPTO_MINALIGN makes those drivers work then so should cra_alignmask. And that would be a relatively easy patch to do. Cheers, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt 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 D67D5C433EF for ; Tue, 12 Apr 2022 09:42:43 +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=gY6rD1W9jyBDDvNvVbfjDdNwOrjQSyABVe0vPGWC1H4=; b=KauUwA1cxmFdTz m8mg9mNd33XejeGCuW1R6Fd9GCtv2Fi4YSDtx8OAmVh1B7yZypTyud+/IwfFTX8xSdUFEoNl/Up+b loz4pwZk2/0nFQuphkQYm+bsB4ewaEX1rCJJwhX0t+F6WmKcTsWn22UyxhXreoMv/nxc2LuTTz1aW lXpasjn628vsRHgmeYotRubo7K4OunqGDaAomNhvU4nPwi6hq5c+8N920ktHP0xfYGNXQXhQs0cfF 99io/dLCeFO9HHcLhS4oou0d5RHhTeczol5nFbMWFJMOykC94/89OLr0uFvnKKS3g2i4ME4DQ13kc zS/RQmcYUIpFTcfYfZtg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1neD1e-00CzoV-2l; Tue, 12 Apr 2022 09:41:30 +0000 Received: from helcar.hmeau.com ([216.24.177.18] helo=fornost.hmeau.com) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1neD1b-00Czm2-0I for linux-arm-kernel@lists.infradead.org; Tue, 12 Apr 2022 09:41:28 +0000 Received: from gwarestrin.arnor.me.apana.org.au ([192.168.103.7]) by fornost.hmeau.com with smtp (Exim 4.94.2 #2 (Debian)) id 1neD17-001sqd-Uh; Tue, 12 Apr 2022 19:40:59 +1000 Received: by gwarestrin.arnor.me.apana.org.au (sSMTP sendmail emulation); Tue, 12 Apr 2022 17:40:58 +0800 Date: Tue, 12 Apr 2022 17:40:58 +0800 From: Herbert Xu To: Catalin Marinas Cc: Ard Biesheuvel , Will Deacon , Marc Zyngier , Arnd Bergmann , Greg Kroah-Hartman , Andrew Morton , Linus Torvalds , linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, "David S. Miller" Subject: Re: [PATCH 07/10] crypto: Use ARCH_DMA_MINALIGN instead of ARCH_KMALLOC_MINALIGN Message-ID: References: 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-20220412_024127_080010_D224F208 X-CRM114-Status: GOOD ( 14.34 ) 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 Tue, Apr 12, 2022 at 10:32:58AM +0100, Catalin Marinas wrote: > > At a quick grep, most cra_alignmask values are currently 15 or smaller. > I'm not convinced the driver needs to know about the CPU cache > alignment. We could set cra_alignmask to CRYPTO_MINALIGN but that would > incur unnecessary overhead via function like setkey_unaligned() when the > arch_kmalloc_minalign() was already sufficient for DMA safety. > > Maybe I miss some use-cases or I focus too much on DMA safety. The alignment was never designed for DMA. It's mainly for CPUs that provide accelerated instructions that require a certain amount of alignment, most commonly 16 bytes. Therefore CRYPTO_MINALIGN was never meant to be a guarantee for DMA alignment. Any drivers relying on this is simply broken. I understand that on ARM for historical reasons you have had a situation that CRYPTO_MINALIGN happened to be large enough to guarantee DMA alignment. I totally agree with your patch to try to fix this but it should not penalise other architectures and raise the CRYPTO_MINALIGN unnecessarily. I think if CRYPTO_MINALIGN makes those drivers work then so should cra_alignmask. And that would be a relatively easy patch to do. Cheers, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel