From: Eugenio Pérez <eperezma@xxxxxxxxxx>
[ Upstream commit b4cca6d48eb3fa6f0d9caba4329b1a2b0ff67a77 ]
Starting from an used_idx different than 0 is needed in use cases like
virtual machine migration. Not doing so and letting the caller set an
avail idx different than 0 causes destination device to try to use old
buffers that source driver already recover and are not available
anymore.
Since vdpa_sim does not support receive inflight descriptors as a
destination of a migration, let's set both avail_idx and used_idx the
same at vq start. This is how vhost-user works in a
VHOST_SET_VRING_BASE call.
Although the simple fix is to set last_used_idx at vdpasim_set_vq_state,
it would be reset at vdpasim_queue_ready. The last_avail_idx case is
fixed with commit 0e84f918fac8 ("vdpa_sim: not reset state in
vdpasim_queue_ready"). Since the only option is to make it equal to
last_avail_idx, adding the only change needed here.
This was discovered and tested live migrating the vdpa_sim_net device.
Fixes: 2c53d0f64c06 ("vdpasim: vDPA device simulator")
Reviewed-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
Signed-off-by: Eugenio Pérez <eperezma@xxxxxxxxxx>
Message-Id: <20230302181857.925374-1-eperezma@xxxxxxxxxx>
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/vdpa/vdpa_sim/vdpa_sim.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
index eeda45fbba258..3ccefa58e405c 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
@@ -75,6 +75,17 @@ static void vdpasim_queue_ready(struct vdpasim *vdpasim, unsigned int idx)
(uintptr_t)vq->device_addr);
vq->vring.last_avail_idx = last_avail_idx;
+
+ /*
+ * Since vdpa_sim does not support receive inflight descriptors as a
+ * destination of a migration, let's set both avail_idx and used_idx
+ * the same at vq start. This is how vhost-user works in a
+ * VHOST_SET_VRING_BASE call.
+ *
+ * Although the simple fix is to set last_used_idx at
+ * vdpasim_set_vq_state, it would be reset at vdpasim_queue_ready.
+ */
+ vq->vring.last_used_idx = last_avail_idx;
vq->vring.notify = vdpasim_vq_notify;
}
--
2.39.2
