On 5/9/23 1:46 AM, Stefano Garzarella wrote:

On Mon, Apr 24, 2023 at 03:50:30PM -0700, Shannon Nelson via 
Virtualization wrote:

quoted

Use the right structs for PACKED or split vqs when setting and
getting the vring base.

Signed-off-by: Shannon Nelson <redacted>
---
drivers/vhost/vhost.c | 18 +++++++++++++-----
drivers/vhost/vhost.h |  8 ++++++--
2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index f11bdbe4c2c5..f64efda48f21 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c

@@ -1633,17 +1633,25 @@ long vhost_vring_ioctl(struct vhost_dev *d, 

unsigned int ioctl, void __user *arg
                      r = -EFAULT;
                      break;
              }
-              if (s.num > 0xffff) {
-                      r = -EINVAL;
-                      break;
+              if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+                      vq->last_avail_idx = s.num & 0xffff;
+                      vq->last_used_idx = (s.num >> 16) & 0xffff;
+              } else {
+                      if (s.num > 0xffff) {
+                              r = -EINVAL;
+                              break;
+                      }
+                      vq->last_avail_idx = s.num;
              }
-              vq->last_avail_idx = s.num;
              /* Forget the cached index value. */
              vq->avail_idx = vq->last_avail_idx;
              break;
      case VHOST_GET_VRING_BASE:
              s.index = idx;
-              s.num = vq->last_avail_idx;
+              if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+                      s.num = (u32)vq->last_avail_idx | 
((u32)vq->last_used_idx << 16);
+              else
+                      s.num = vq->last_avail_idx;

The changes LGTM, but since we are changing the UAPI, should we
update the documentation of VHOST_SET_VRING_BASE and
VHOST_GET_VRING_BASE in include/uapi/linux/vhost.h?

Correct me if I'm wrong, but I don't think we're changing anything in 
the UAPI here, just fixing code to work correctly with what is already 
happening.

sln

Thanks,
Stefano

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