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UPSTREAM: vring: Use the DMA API on Xen

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Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
(cherry picked from commit 78fe39872378b0bef00a91181f1947acb8a08500)
Bug: 121166534
Test: Ran cuttlefish with android-4.4 + VSOCKETS, VMWARE_VMCI_VSOCKETS
Signed-off-by: Alistair Strachan <astrachan@google.com>

Change-Id: Ibf85aad139f319354cd2ee8833ca9434c15640d8
This commit is contained in:
Andy Lutomirski 2016-02-02 21:46:40 -08:00 • committed by Alistair Strachan
parent 4323356bac
commit 77facbcf65
1 changed files with 12 additions and 0 deletions
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12
drivers/virtio/virtio_ring.c
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@ -25,6 +25,7 @@
#include <linux/hrtimer.h> #include <linux/hrtimer.h>
#include <linux/kmemleak.h> #include <linux/kmemleak.h>
#include <linux/dma-mapping.h> #include <linux/dma-mapping.h>
#include <xen/xen.h>
#ifdef DEBUG #ifdef DEBUG
/* For development, we want to crash whenever the ring is screwed. */ /* For development, we want to crash whenever the ring is screwed. */
@ -131,6 +132,17 @@ struct vring_virtqueue {
static bool vring_use_dma_api(struct virtio_device *vdev) 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; return false;
} }