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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 69FFCC43387 for ; Thu, 10 Jan 2019 14:26:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 33675214DA for ; Thu, 10 Jan 2019 14:26:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728175AbfAJO0m (ORCPT ); Thu, 10 Jan 2019 09:26:42 -0500 Received: from 8bytes.org ([81.169.241.247]:56652 "EHLO theia.8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727768AbfAJO0m (ORCPT ); Thu, 10 Jan 2019 09:26:42 -0500 Received: by theia.8bytes.org (Postfix, from userid 1000) id E1B2D22E; Thu, 10 Jan 2019 15:26:40 +0100 (CET) Date: Thu, 10 Jan 2019 15:26:40 +0100 From: Joerg Roedel To: Christoph Hellwig Cc: "Michael S . Tsirkin" , Jason Wang , Konrad Rzeszutek Wilk , Jens Axboe , virtualization@lists.linux-foundation.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, jfehlig@suse.com, jon.grimm@amd.com, brijesh.singh@amd.com Subject: Re: [PATCH 0/3] Fix virtio-blk issue with SWIOTLB Message-ID: <20190110142640.GA5825@8bytes.org> References: <20190110134433.15672-1-joro@8bytes.org> <20190110135952.GC9255@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190110135952.GC9255@lst.de> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Hi Christoph, On Thu, Jan 10, 2019 at 02:59:52PM +0100, Christoph Hellwig wrote: > On Thu, Jan 10, 2019 at 02:44:30PM +0100, Joerg Roedel wrote: > > The problem is a limitation of the SWIOTLB implementation, > > which does not support allocations larger than 256kb. When > > the virtio-blk driver tries to read/write a block larger > > than that, the allocation of the dma-handle fails and an IO > > error is reported. > > s/allocations/mappings/, right? We don't use the swiotlb > buffer for the coherent allocations anymore, and I don't think > virtio-blk uses them anyway. 'Allocation' in the sense that there are address ranges allocated, not memory, but mappings would also be right. > I really don't like the fact that we hardcode swiotlb specific. > This needs to be indirect through the dma ops or struct device, > as various iommu implementations also have limits (although > usually much larger ones). I though about exposing it through DMA-API, but didn't go that route as I didn't want to extend a generic API for some SWIOTLB specifics. But if there are more implementations that have a size limitation it makes certainly sense to put it into the DMA-API. I'll change that in the next version. Thanks, Joerg