[RFC PATCH] virtio_ring: Use DMA API if guest memory is encrypted

[Thiago Jung Bauermann]

The host can't access the guest memory when it's encrypted, so using
regular memory pages for the ring isn't an option. Go through the DMA API.

Signed-off-by: Thiago Jung Bauermann <bauerman@xxxxxxxxxxxxx>
---
 drivers/virtio/virtio_ring.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index cd7e755484e3..321a27075380 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -259,8 +259,11 @@ static bool vring_use_dma_api(struct virtio_device *vdev)
 	 * 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.
+	 *
+	 * Also, if guest memory is encrypted the host can't access
+	 * it directly. In this case, we'll need to use the DMA API.
 	 */
-	if (xen_domain())
+	if (xen_domain() || sev_active())
 		return true;

 	return false;