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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 5D5C1C3A5A5 for ; Thu, 5 Sep 2019 06:06:37 +0000 (UTC) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org [140.211.169.12]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 2D592217D7 for ; Thu, 5 Sep 2019 06:06:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2D592217D7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from mail.linux-foundation.org (localhost [127.0.0.1]) by mail.linuxfoundation.org (Postfix) with ESMTP id 0C18FDA7; Thu, 5 Sep 2019 06:06:37 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 4479149F for ; Thu, 5 Sep 2019 06:06:35 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 523D8A9 for ; Thu, 5 Sep 2019 06:06:33 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 27DF868AFE; Thu, 5 Sep 2019 08:06:28 +0200 (CEST) Date: Thu, 5 Sep 2019 08:06:27 +0200 From: Christoph Hellwig To: David Rientjes Subject: Re: [bug] __blk_mq_run_hw_queue suspicious rcu usage Message-ID: <20190905060627.GA1753@lst.de> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) Cc: Jens Axboe , Tom Lendacky , Brijesh Singh , x86@kernel.org, linux-kernel@vger.kernel.org, Ming Lei , iommu@lists.linux-foundation.org, Peter Gonda , Christoph Hellwig , Jianxiong Gao X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.12 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 Sender: iommu-bounces@lists.linux-foundation.org Errors-To: iommu-bounces@lists.linux-foundation.org On Wed, Sep 04, 2019 at 02:40:44PM -0700, David Rientjes wrote: > Hi Christoph, Jens, and Ming, > > While booting a 5.2 SEV-enabled guest we have encountered the following > WARNING that is followed up by a BUG because we are in atomic context > while trying to call set_memory_decrypted: Well, this really is a x86 / DMA API issue unfortunately. Drivers are allowed to do GFP_ATOMIC dma allocation under locks / rcu critical sections and from interrupts. And it seems like the SEV case can't handle that. We have some semi-generic code to have a fixed sized pool in kernel/dma for non-coherent platforms that have similar issues that we could try to wire up, but I wonder if there is a better way to handle the issue, so I've added Tom and the x86 maintainers. Now independent of that issue using DMA coherent memory for the nvme PRPs/SGLs doesn't actually feel very optional. We could do with normal kmalloc allocations and just sync it to the device and back. I wonder if we should create some general mempool-like helpers for that. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu