Re: [RFC V4 PATCH 7/8] vhost: packed ring support

On 2018年05月23日 15:17, Wei Xu wrote:

On Wed, May 23, 2018 at 09:39:28AM +0800, Jason Wang wrote:

quoted

On 2018年05月23日 00:54, Wei Xu wrote:

quoted

On Wed, May 16, 2018 at 08:32:20PM +0800, Jason Wang wrote:

quoted

Signed-off-by: Jason Wang <redacted>
---
  drivers/vhost/net.c   |   3 +-
  drivers/vhost/vhost.c | 539 ++++++++++++++++++++++++++++++++++++++++++++++----
  drivers/vhost/vhost.h |   8 +-
  3 files changed, 513 insertions(+), 37 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 8304c30..f2a0f5b 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c

@@ -1358,6 +1382,8 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
  			break;
  		}
  		vq->last_avail_idx = s.num;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			vq->avail_wrap_counter = s.num >> 31;
  		/* Forget the cached index value. */
  		vq->avail_idx = vq->last_avail_idx;
  		break;

@@ -1366,6 +1392,8 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
  		s.num = vq->last_avail_idx;
  		if (copy_to_user(argp, &s, sizeof s))
  			r = -EFAULT;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			s.num |= vq->avail_wrap_counter << 31;
  		break;
  	case VHOST_SET_VRING_ADDR:
  		if (copy_from_user(&a, argp, sizeof a)) {

'last_used_idx' also needs to be saved/restored here.

I have figured out the root cause of broken device after reloading
'virtio-net' module, all indices have been reset for a reloading but
'last_used_idx' is not properly reset in this case. This confuses
handle_rx()/tx().

Wei

Good catch, so we probably need a new ioctl to sync between qemu and vhost.

Something like VHOST_SET/GET_USED_BASE.

Sure, or can we expand 'vhost_vring_state' to keep them done in a bunch?

It's port of uapi, so we can't.

Thanks

quoted

Thanks

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