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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 EA2D8C76191 for ; Thu, 25 Jul 2019 11:54:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CC7DA2238C for ; Thu, 25 Jul 2019 11:54:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728588AbfGYLyB (ORCPT ); Thu, 25 Jul 2019 07:54:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49732 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726531AbfGYLyB (ORCPT ); Thu, 25 Jul 2019 07:54:01 -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 7331D300CA39; Thu, 25 Jul 2019 11:54:00 +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 45E2960C05; Thu, 25 Jul 2019 11:53:51 +0000 (UTC) Subject: Re: [PATCH 2/2] virtio/virtio_ring: Fix the dma_max_mapping_size call To: Christoph Hellwig , Robin Murphy Cc: 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> From: Auger Eric Message-ID: Date: Thu, 25 Jul 2019 13:53:49 +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: <20190723153851.GE720@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 [10.5.110.42]); Thu, 25 Jul 2019 11:54:00 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 7/23/19 5:38 PM, Christoph Hellwig wrote: > On Mon, Jul 22, 2019 at 04:36:09PM +0100, Robin Murphy wrote: >>> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c >>> index c8be1c4f5b55..37c143971211 100644 >>> --- a/drivers/virtio/virtio_ring.c >>> +++ b/drivers/virtio/virtio_ring.c >>> @@ -262,7 +262,7 @@ size_t virtio_max_dma_size(struct virtio_device *vdev) >>> { >>> size_t max_segment_size = SIZE_MAX; >>> - if (vring_use_dma_api(vdev)) >>> + if (vring_use_dma_api(vdev) && vdev->dev.dma_mask) >> >> Hmm, might it make sense to roll that check up into vring_use_dma_api() >> itself? After all, if the device has no mask then it's likely that other >> DMA API ops wouldn't really work as expected either. > > Makes sense to me. > 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? Thanks Eric