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 X-Spam-Level: X-Spam-Status: No, score=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BFE4CC4320A for ; Wed, 11 Aug 2021 05:54:24 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 159A86101D for ; Wed, 11 Aug 2021 05:54:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 159A86101D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 5767D6B0071; Wed, 11 Aug 2021 01:54:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 526246B0072; Wed, 11 Aug 2021 01:54:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 414DB6B0073; Wed, 11 Aug 2021 01:54:23 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0108.hostedemail.com [216.40.44.108]) by kanga.kvack.org (Postfix) with ESMTP id 21C096B0071 for ; Wed, 11 Aug 2021 01:54:23 -0400 (EDT) Received: from smtpin40.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id AABA08249980 for ; Wed, 11 Aug 2021 05:54:22 +0000 (UTC) X-FDA: 78461734764.40.3684034 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf30.hostedemail.com (Postfix) with ESMTP id 8E3CDE0085FA for ; Wed, 11 Aug 2021 05:54:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=ximqsP9eH81bjVTaLK5J8CTiAXmX0UXkr88CH/kujB0=; b=cqQCYTwO/n7keDf+DqW61O3WA7 zquidGQy0kxeH+7gbrGWVqsa7V3686YeaBXzKuBAdl0fJoxWBxVuoRsb9QKKYiY+5VgPvDgyk0TGc lBAmlaWNvUXrFE5ahOzTMmz0/4HEIqdFhYOnYKylUxwF+UpWhX6c9G1wffuBtd9ANpeez5ToumXOG a11j6UgDrHIFNB9OMZD1kbBTGiBhnLqIZ4g+7KHW2ZpGrQd59c4Rwrv/isWwFomaTqGtw8FYdlSHj Rz629UwJJ/E2PrQNXA73arwYJKoZ6UyU+9wskQSPTTVYPbFdks/jZISMTGOLgI/WeNmwI7azg17na ZQzT/Z+w==; Received: from hch by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1mDhAf-00D27X-99; Wed, 11 Aug 2021 05:53:05 +0000 Date: Wed, 11 Aug 2021 06:52:57 +0100 From: Christoph Hellwig To: Tom Lendacky Cc: Baoquan He , Robin Murphy , Christoph Hellwig , brijesh.singh@amd.com, x86@kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, rppt@linux.ibm.com, linux-mm@kvack.org, iommu@lists.linux-foundation.org, rientjes@google.com Subject: Re: [PATCH RFC 0/2] dma-pool: allow user to disable atomic pool Message-ID: References: <20210624052010.5676-1-bhe@redhat.com> <20210624092930.GA802261@MiWiFi-R3L-srv> <8b3d4e02-6e94-ad59-a480-fed8e55c009a@arm.com> <20210805065410.GA2051@MiWiFi-R3L-srv> <5df93c4e-ffdd-88c5-db4a-1a09826d047a@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5df93c4e-ffdd-88c5-db4a-1a09826d047a@amd.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 8E3CDE0085FA Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=cqQCYTwO; dmarc=none; spf=none (imf30.hostedemail.com: domain of BATV@casper.srs.infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=BATV@casper.srs.infradead.org X-Stat-Signature: 8es9twafxr871mdejue94ay4ezyew77q X-HE-Tag: 1628661261-756795 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Aug 10, 2021 at 03:52:25PM -0500, Tom Lendacky via iommu wrote: > I think the atomic pool is used by the NVMe driver. My understanding is > that driver will do a dma_alloc_coherent() from interrupt context, so it > needs to use GFP_ATOMIC. The pool was created because dma_alloc_coherent() > would perform a set_memory_decrypted() call, which can sleep. The pool > eliminates that issue (David can correct me if I got that wrong). Not just the NVMe driver. We have plenty of drivers doing that, just do a quick grep for dma_alloc_* dma_poll_alloc, dma_pool_zalloc with GFP_ATOMIC (and that won't even find multi-line strings).