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 DCED3C433EF for ; Tue, 12 Apr 2022 12:45:25 +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=jIBT22Jh4RDnQqkL6AaloIw1vehWHJtd9+CWUp6DA4U=; b=SkIFLpNSM0hv7J WyRC6di/lIZI6iMjHUNGtjldKI+9V6yj20L97/5W094Yq/MHuafQJQdbpjZ+fEnoq04nXFRoZD4R4 HaP5IqIEPlrNVVyCwG9ZZ4OHvP64cojg1fBELO2MSVmrXbVaWWY4dtDydkjmTF0k6P5hb4tKj5Ovt eZJA8hvoLdgEpkqd3QQmNLozPf/MhwlYn28FRzg3zmYJxaQDvzpGDfFdr1UITdlEtK5w7/Nojw2US sfzb2ETyFtF6GWuGEk5KAqdcSI0ez8f/s+cPhbV4XAK0gHhtb6S95JrCTBKZLF6dp2jxUEdYkh7+r egfTk+pyuXofI+7RVT3Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1neFsL-00EFmP-JI; Tue, 12 Apr 2022 12:44:05 +0000 Received: from ams.source.kernel.org ([145.40.68.75]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1neFg8-00E9hM-Fm for linux-arm-kernel@lists.infradead.org; Tue, 12 Apr 2022 12:31:30 +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 ams.source.kernel.org (Postfix) with ESMTPS id 1ACFCB81D2E; Tue, 12 Apr 2022 12:31:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8FDBAC385A5; Tue, 12 Apr 2022 12:31:23 +0000 (UTC) Date: Tue, 12 Apr 2022 13:31:20 +0100 From: Catalin Marinas To: Herbert Xu 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_053128_733682_3631C989 X-CRM114-Status: GOOD ( 20.38 ) 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 06:18:46PM +0800, Herbert Xu wrote: > On Tue, Apr 12, 2022 at 11:02:54AM +0100, Catalin Marinas wrote: > > This series does not penalise any architecture. It doesn't even make > > arm64 any worse than it currently is. > > Right, the patch as it stands doesn't change anything. However, > it is also broken as it stands. As I said before, CRYPTO_MINALIGN > is not something that is guaranteed by the Crypto API, it is simply > a statement of whatever kmalloc returns. I agree that CRYPTO_MINALIGN is not guaranteed by the Crypto API. What I'm debating is the intended use for CRYPTO_MINALIGN in some (most?) of the drivers. It's not just about kmalloc() but also a build-time offset of buffers within structures to guarantee DMA safety. This can't be fixed by cra_alignmask. We could leave CRYPTO_MINALIGN as ARCH_KMALLOC_MINALIGN and that matches it being just a statement of the kmalloc() minimum alignment. But since it is also overloaded with the DMA in-structure offset alignment, we'd need a new CRYPTO_DMA_MINALIGN (and _ATTR) to annotate those structures. I have a suspicion there'll be fewer of the original CRYPTO_MINALIGN uses left, hence my approach to making this bigger from the start. There's also Ard's series introducing CRYPTO_REQ_MINALIGN while leaving CRYPT_MINALIGN for DMA-safe offsets (IIUC): https://lore.kernel.org/r/20220406142715.2270256-1-ardb@kernel.org > So if kmalloc is no longer returning CRYPTO_MINALIGN-aligned > memory, then those drivers that need this alignment for DMA > will break anyway. No. As per one of my previous emails, kmalloc() will preserve the DMA alignment for an SoC even if smaller than CRYPTO_MINALIGN (or a new CRYPTO_DMA_MINALIGN). Since kmalloc() returns DMA-safe pointers and CRYPTO_MINALIGN (or a new CRYPTO_DMA_MINALIGN) is DMA-safe, so would an offset from a pointer returned by kmalloc(). > If you want the Crypto API to guarantee alignment over and above > that returned by kmalloc, the correct way is to use cra_alignmask. For kmalloc(), this would work, but for the current CRYPTO_MINALIGN_ATTR uses it won't. Thanks. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel