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,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 06327C7618B for ; Thu, 25 Jul 2019 16:32:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D00D422C7C for ; Thu, 25 Jul 2019 16:32:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729303AbfGYQcV (ORCPT ); Thu, 25 Jul 2019 12:32:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57516 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726087AbfGYQcV (ORCPT ); Thu, 25 Jul 2019 12:32:21 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id F144A86679; Thu, 25 Jul 2019 16:32:20 +0000 (UTC) Received: from [10.36.116.102] (ovpn-116-102.ams2.redhat.com [10.36.116.102]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7EA3E60C05; Thu, 25 Jul 2019 16:32:16 +0000 (UTC) Subject: Re: [PATCH 2/2] virtio/virtio_ring: Fix the dma_max_mapping_size call To: Christoph Hellwig Cc: Robin Murphy , eric.auger.pro@gmail.com, m.szyprowski@samsung.com, mst@redhat.com, jasowang@redhat.com, virtualization@lists.linux-foundation.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org References: <20190722145509.1284-1-eric.auger@redhat.com> <20190722145509.1284-3-eric.auger@redhat.com> <20190723153851.GE720@lst.de> <20190725130416.GA4992@lst.de> From: Auger Eric Message-ID: <11b7b5e4-2de7-2089-57d2-d0a138f94376@redhat.com> Date: Thu, 25 Jul 2019 18:32:14 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190725130416.GA4992@lst.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Thu, 25 Jul 2019 16:32:21 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Christoph, Michael, On 7/25/19 3:04 PM, Christoph Hellwig wrote: > On Thu, Jul 25, 2019 at 01:53:49PM +0200, Auger Eric wrote: >> I am confused: if vring_use_dma_api() returns false if the dma_mask is >> unset (ie. vring_use_dma_api() returns false), the virtio-blk-pci device >> will not be able to get translated addresses and won't work properly. >> >> The patch above allows the dma api to be used and only influences the >> max_segment_size and it works properly. >> >> So is it normal the dma_mask is unset in my case? > > Its not normal. I assume you use virtio-nmio? Due to the mess with > the dma_mask being a pointer a lot of subsystems forgot to set a dma > mask up, and oddly enough seem to mostly get away with it. > No the issue is encountered with virtio-blk-pci I think the problem is virtio_max_dma_size() is called from virtblk_probe (virtio_blk.c) on the virtio device and not the actual virtio_pci_device which has a dma_mask set. I don't think the virtio device ever has a dma_mask set. We do not hit the guest crash on the virtio-net-pci device as the virtio-net driver does not call virtio_max_dma_size() on the virtio device. Does fd1068e1860e ("virtio-blk: Consider virtio_max_dma_size() for maximum segment size") call virtio_max_dma_size() on the right device? Thanks Eric