[PATCH v3 8/8] vhost: improve vDPA blk device readiness condition

[Xia, Chenbo]

> -----Original Message-----
> From: Pei, Andy <andy.pei at intel.com>
> Sent: Friday, September 16, 2022 2:17 PM
> To: dev at dpdk.org
> Cc: Xia, Chenbo <chenbo.xia at intel.com>; Xu, Rosen <rosen.xu at intel.com>;
> Huang, Wei <wei.huang at intel.com>; Cao, Gang <gang.cao at intel.com>;
> maxime.coquelin at redhat.com
> Subject: [PATCH v3 8/8] vhost: improve vDPA blk device readiness condition
> 
> In the virtio blk vDPA live migration use case, for the target VM,
> before the live migration process, QEMU will set call fd to all
> queues of vDPA back-end. QEMU and vDPA back-end stand by
> until live migration starts. During live migration process,
> QEMU sets kick fd and new call fd. However, after the kick fd
> is set to the vDPA back-end, the vDPA back-end configures device
> and data path starts. The new call fd will cause some kind of
> "re-configuration", this kind of "re-configuration" cause IO drop.
> After this patch, vDPA back-end configures device after kick fd
> and call fd are well set and make sure no IO drops.
> This patch only impact virtio blk vDPA device and does not impact
> net device.

IIUC, this is an improvement for MQ to make sure all call fds are well-set,
but previously it only makes sure one is well-set. If I am right, the title
and commit message should describe it in better way.

Thanks,
Chenbo

> 
> Signed-off-by: Andy Pei <andy.pei at intel.com>
> Signed-off-by: Huang Wei <wei.huang at intel.com>
> ---
>  lib/vhost/vhost_user.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/vhost/vhost_user.c b/lib/vhost/vhost_user.c
> index 9169cf5..14ff266 100644
> --- a/lib/vhost/vhost_user.c
> +++ b/lib/vhost/vhost_user.c
> @@ -2983,6 +2983,7 @@ static int is_vring_iotlb(struct virtio_net *dev,
>  	uint32_t vdpa_type = 0;
>  	uint32_t request;
>  	uint32_t i;
> +	uint16_t blk_call_fd;
> 
>  	dev = get_device(vid);
>  	if (dev == NULL)
> @@ -3210,9 +3211,15 @@ static int is_vring_iotlb(struct virtio_net *dev,
>  	if (!vdpa_dev)
>  		goto out;
> 
> -	if (vdpa_type == RTE_VHOST_VDPA_DEVICE_TYPE_BLK
> -		&& request != VHOST_USER_SET_VRING_CALL)
> -		goto out;
> +	if (vdpa_type == RTE_VHOST_VDPA_DEVICE_TYPE_BLK) {
> +		if (request == VHOST_USER_SET_VRING_CALL) {
> +			blk_call_fd = ctx.msg.payload.u64 &
> VHOST_USER_VRING_IDX_MASK;
> +			if (blk_call_fd != dev->nr_vring - 1)
> +				goto out;
> +		} else {
> +			goto out;
> +		}
> +	}
> 
>  	if (!(dev->flags & VIRTIO_DEV_VDPA_CONFIGURED)) {
>  		if (vdpa_dev->ops->dev_conf(dev->vid))
> --
> 1.8.3.1