Re: [dpdk-dev] [PATCH v3 15/19] vhost: postpone rings addresses translation

["Yao, Lei A" <lei.a.yao@intel.com>]

Hi, Maxime

> -----Original Message-----
> From: Maxime Coquelin [mailto:maxime.coquelin@redhat.com]
> Sent: Monday, October 16, 2017 6:48 PM
> To: Yao, Lei A <lei.a.yao@intel.com>; 'dev@dpdk.org' <dev@dpdk.org>;
> Horton, Remy <remy.horton@intel.com>; Bie, Tiwei <tiwei.bie@intel.com>;
> 'yliu@fridaylinux.org' <yliu@fridaylinux.org>
> Cc: 'mst@redhat.com' <mst@redhat.com>; 'jfreiman@redhat.com'
> <jfreiman@redhat.com>; 'vkaplans@redhat.com' <vkaplans@redhat.com>;
> 'jasowang@redhat.com' <jasowang@redhat.com>
> Subject: Re: [dpdk-dev] [PATCH v3 15/19] vhost: postpone rings addresses
> translation
> 
> 
> 
> On 10/16/2017 11:47 AM, Maxime Coquelin wrote:
> > Hi Yao,
> >
> > On 10/16/2017 08:23 AM, Yao, Lei A wrote:
> >> Hi, Maxime
> >>
> >> Add one comment:
> >> This issue with virtio-net only occur when I use CPU on socket 1.
> >
> > Thanks for the report.
> > I fail to reproduce for now.
> >
> > What is your qemu command line?
> > Is it reproducible systematically when there is a NUMA reallocation
> > (DPDK on socket 0, QEMU on socket 1)?
> 
> Nevermind, I just reproduced the (an?) issue.
> The issue I reproduce is not linked to NUMA reallocation, but to
> messages sequencing differences between QEMU versions.
> 
> So, I'm not 100% this is the same issue, as you mention it works fine
> when using CPU socket 0.
> 
> The patch "vhost: postpone rings addresses translation" moves rings
> addresses translation at either vring kick or enable time, depending
> on whether protocol features are enabled or not. This has been done
> because we must not interpret ring information as long as the vring is
> not fully initialized.
> 
> While my patch works fine with recent QEMU version, it breaks with older
> ones, like QEMU v2.5. The reason is that on these older versions,
> VHOST_USER_SET_VRING_ENABLE is called once and before
> VHOST_USER_SET_VRING_ADDR. At that time, the ring adresses aren't
> available so the translation is not done. On recent QEMU versions,
> we receive VHOST_USER_SET_VRING_ENABLE also after having received
> the rings addresses, so it works fine.
> 
> The below fix consists in performing the rings addresses translation
> also when handling VHOST_USER_SET_VRING_ADDR if ring has already been
> enabled.
> 
> I'll post a formal patch later today or tomorrow morning after having
> tested it more conscientiously. Let me know if it fixes your issue.
> 
> Thanks,
> Maxime
> 
Thanks for your quick fix. I try your patch and it can totally work at my side for virtio-net.
I tested it with Qemu 2.5~2.7, 2.10. 
The previous info about it can work on numa 0 is a misleading info. Because
I use qemu 2.10 for some special test at that time. So it can work. 

BRs
Lei
> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
> index 76c4eeca5..1f6cba4b9 100644
> --- a/lib/librte_vhost/vhost_user.c
> +++ b/lib/librte_vhost/vhost_user.c
> @@ -372,33 +372,6 @@ ring_addr_to_vva(struct virtio_net *dev, struct
> vhost_virtqueue *vq,
>          return qva_to_vva(dev, ra);
>   }
> 
> -/*
> - * The virtio device sends us the desc, used and avail ring addresses.
> - * This function then converts these to our address space.
> - */
> -static int
> -vhost_user_set_vring_addr(struct virtio_net *dev, VhostUserMsg *msg)
> -{
> -       struct vhost_virtqueue *vq;
> -       struct vhost_vring_addr *addr = &msg->payload.addr;
> -
> -       if (dev->mem == NULL)
> -               return -1;
> -
> -       /* addr->index refers to the queue index. The txq 1, rxq is 0. */
> -       vq = dev->virtqueue[msg->payload.addr.index];
> -
> -       /*
> -        * Rings addresses should not be interpreted as long as the ring
> is not
> -        * started and enabled
> -        */
> -       memcpy(&vq->ring_addrs, addr, sizeof(*addr));
> -
> -       vring_invalidate(dev, vq);
> -
> -       return 0;
> -}
> -
>   static struct virtio_net *
>   translate_ring_addresses(struct virtio_net *dev, int vq_index)
>   {
> @@ -464,6 +437,43 @@ translate_ring_addresses(struct virtio_net *dev,
> int vq_index)
>   }
> 
>   /*
> + * The virtio device sends us the desc, used and avail ring addresses.
> + * This function then converts these to our address space.
> + */
> +static int
> +vhost_user_set_vring_addr(struct virtio_net **pdev, VhostUserMsg *msg)
> +{
> +       struct vhost_virtqueue *vq;
> +       struct vhost_vring_addr *addr = &msg->payload.addr;
> +       struct virtio_net *dev = *pdev;
> +
> +       if (dev->mem == NULL)
> +               return -1;
> +
> +       /* addr->index refers to the queue index. The txq 1, rxq is 0. */
> +       vq = dev->virtqueue[msg->payload.addr.index];
> +
> +       /*
> +        * Rings addresses should not be interpreted as long as the ring
> is not
> +        * started and enabled
> +        */
> +       memcpy(&vq->ring_addrs, addr, sizeof(*addr));
> +
> +       vring_invalidate(dev, vq);
> +
> +       if (vq->enabled && (dev->features &
> +                               (1ULL << VHOST_USER_F_PROTOCOL_FEATURES))) {
> +               dev = translate_ring_addresses(dev,
> msg->payload.state.index);
> +               if (!dev)
> +                       return -1;
> +
> +               *pdev = dev;
> +       }
> +
> +       return 0;
> +}
> +
> +/*
>    * The virtio device sends us the available ring last used index.
>    */
>   static int
> @@ -1273,7 +1283,7 @@ vhost_user_msg_handler(int vid, int fd)
>                  vhost_user_set_vring_num(dev, &msg);
>                  break;
>          case VHOST_USER_SET_VRING_ADDR:
> -               vhost_user_set_vring_addr(dev, &msg);
> +               vhost_user_set_vring_addr(&dev, &msg);
>                  break;
>          case VHOST_USER_SET_VRING_BASE:
>                  vhost_user_set_vring_base(dev, &msg);