diff mbox

[v7,9/9] vring: Use the DMA API on Xen

Message ID a5b072806984a0fceb4f4d33cbeb1cea7d881e8b.1454477782.git.luto@kernel.org
State New, archived
Headers show

Commit Message

Andy Lutomirski Feb. 3, 2016, 5:46 a.m. UTC
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 drivers/virtio/virtio_ring.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

Comments

David Vrabel Feb. 3, 2016, 9:49 a.m. UTC | #1
On 03/02/16 05:46, Andy Lutomirski wrote:
> Signed-off-by: Andy Lutomirski <luto@kernel.org>

You forgot the previous Reviewed-by tags.

David
Andy Lutomirski Feb. 4, 2016, 5:49 p.m. UTC | #2
On Wed, Feb 3, 2016 at 1:49 AM, David Vrabel <david.vrabel@citrix.com> wrote:
> On 03/02/16 05:46, Andy Lutomirski wrote:
>> Signed-off-by: Andy Lutomirski <luto@kernel.org>
>
> You forgot the previous Reviewed-by tags.

Whoops.  If I send another version, they'll be there.

>
> David
diff mbox

Patch

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index e46d08107a50..5c802d47892c 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -25,6 +25,7 @@ 
 #include <linux/hrtimer.h>
 #include <linux/kmemleak.h>
 #include <linux/dma-mapping.h>
+#include <xen/xen.h>
 
 #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(struct virtio_device *vdev)
 {
+	/*
+	 * 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;
 }