Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
---
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 c169c6444637..305c05cc249a 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -47,6 +47,18 @@
static bool vring_use_dma_api(void)
{
+#if defined(CONFIG_X86) && defined(CONFIG_XEN)
+ /*
+ * 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.
+ */
+ return static_cpu_has(X86_FEATURE_XENPV);
+#endif
+
return false;
}
--
2.5.0
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