From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753777AbcBASBy (ORCPT ); Mon, 1 Feb 2016 13:01:54 -0500 Received: from mail.kernel.org ([198.145.29.136]:48757 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753503AbcBASBS (ORCPT ); Mon, 1 Feb 2016 13:01:18 -0500 From: Andy Lutomirski To: "Michael S. Tsirkin" Cc: Benjamin Herrenschmidt , David Woodhouse , "linux-kernel@vger.kernel.org" , "David S. Miller" , sparclinux@vger.kernel.org, Joerg Roedel , Christian Borntraeger , Cornelia Huck , Sebastian Ott , Paolo Bonzini , Christoph Hellwig , KVM , Martin Schwidefsky , linux-s390 , Linux Virtualization , David Vrabel , Stefano Stabellini , xen-devel@lists.xenproject.org, Andy Lutomirski Subject: [PATCH v6 9/9] vring: Use the DMA API on Xen Date: Mon, 1 Feb 2016 10:00:59 -0800 Message-Id: <41aeb1bd026494e277ea5827d99df4a4f41b8b8f.1454349471.git.luto@kernel.org> X-Mailer: git-send-email 2.5.0 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Signed-off-by: Andy Lutomirski --- drivers/virtio/virtio_ring.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index cf2840c7e500..2a921e5b1809 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -25,6 +25,7 @@ #include #include #include +#include #ifdef DEBUG /* For development, we want to crash whenever the ring is screwed. */ @@ -136,6 +137,17 @@ struct vring_virtqueue { static bool vring_use_dma_api(const struct vring_virtqueue *vq) { + /* + * In theory, it's possible to have a buggy QEMU-supposed + * emulated Q35 IOMMU and Xen enabled at the same time. On + * such a configuration, virtio has never worked and will + * not work without an even larger kludge. Instead, enable + * the DMA API if we're a Xen guest, which at least allows + * all of the sensible Xen configurations to work correctly. + */ + if (xen_domain()) + return true; + return false; } -- 2.5.0