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 smtp3.osuosl.org (smtp3.osuosl.org [140.211.166.136]) (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 66898C433EF for ; Thu, 27 Jan 2022 10:08:58 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp3.osuosl.org (Postfix) with ESMTP id EF62860F3B; Thu, 27 Jan 2022 10:08:57 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp3.osuosl.org ([127.0.0.1]) by localhost (smtp3.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id ZHyfF_0tgxmD; Thu, 27 Jan 2022 10:08:57 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp3.osuosl.org (Postfix) with ESMTPS id CC1BE60B79; Thu, 27 Jan 2022 10:08:56 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 9603CC0011; Thu, 27 Jan 2022 10:08:56 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [IPv6:2605:bc80:3010::137]) by lists.linuxfoundation.org (Postfix) with ESMTP id CF48DC000B for ; Thu, 27 Jan 2022 10:08:54 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id C4C71402BB for ; Thu, 27 Jan 2022 10:08:54 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id ap2HRmsdgMkA for ; Thu, 27 Jan 2022 10:08:53 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.8.0 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by smtp4.osuosl.org (Postfix) with ESMTPS id 877CD402B7 for ; Thu, 27 Jan 2022 10:08:53 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 5F33268AA6; Thu, 27 Jan 2022 11:08:48 +0100 (CET) Date: Thu, 27 Jan 2022 11:08:48 +0100 From: Christoph Hellwig To: Robin Murphy Subject: Re: [RFC][DISCUSSION] dma-mapping: allocating noncoherent buffer without mapping Message-ID: <20220127100848.GC15004@lst.de> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>, iommu@lists.linux-foundation.org, Christoph Hellwig X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Wed, Jan 26, 2022 at 01:08:04PM +0000, Robin Murphy wrote: > This doesn't make sense to me. The point of dma_alloc_* is you get back a > dedicated DMA buffer which can then be used at any time. In the noncoherent > case you have to put in explicit dma_sync_*() calls around accesses when > the CPU or device is expected to have updated the buffer contents, but it's > still fundamentally the same paradigm. Exactly. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu