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Re: [libvirt] [PATCHv3 07/11] qemu: Allow multiple vhost-net openings



On 05/16/2013 08:49 AM, Michal Privoznik wrote:
> With multiqueue network feature, we are advised to pass multiple
> vhost-net FDs as well. The ratio should be 1:1. Therefore we must
> alter the qemuOpenVhostNet function to allow that.
> ---
>  src/qemu/qemu_command.c | 60 ++++++++++++++++++++++++++++++++++++-------------
>  src/qemu/qemu_command.h |  3 ++-
>  src/qemu/qemu_hotplug.c | 12 ++++++----
>  3 files changed, 54 insertions(+), 21 deletions(-)
>
> diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
> index a053d49..ec66a33 100644
> --- a/src/qemu/qemu_command.c
> +++ b/src/qemu/qemu_command.c
> @@ -405,17 +405,34 @@ cleanup:
>  }
>  
>  
> +/**
> + * qemuOpenVhostNet:
> + * @def: domain definition
> + * @net: network definition
> + * @qemuCaps: qemu binary capabilities
> + * @vhostfd: array of opened vhost-net device
> + * @vhostfdSize: size of @vhostfd array


"number of file descriptors in ..."

(since "size" might be mistaken as "size in bytes". I agree that
wouldn't make sense to me, but...)


> + *
> + * Open vhost-net, multiple times - if requested.
> + * In case, no vhost-net is needed, @vhostfdSize is set to 0
> + * and 0 is returned.
> + *
> + * Returns: 0 on success
> + *         -1 on failure
> + */
>  int
>  qemuOpenVhostNet(virDomainDefPtr def,
>                   virDomainNetDefPtr net,
>                   virQEMUCapsPtr qemuCaps,
> -                 int *vhostfd)
> +                 int *vhostfd,
> +                 int *vhostfdSize)
>  {
> -    *vhostfd = -1;   /* assume we won't use vhost */
> +    int i;
>  
>      /* If the config says explicitly to not use vhost, return now */
>      if (net->driver.virtio.name == VIR_DOMAIN_NET_BACKEND_TYPE_QEMU) {
> -       return 0;
> +        *vhostfdSize = 0;
> +        return 0;
>      }
>  
>      /* If qemu doesn't support vhost-net mode (including the -netdev command
> @@ -430,6 +447,7 @@ qemuOpenVhostNet(virDomainDefPtr def,
>                                     "this QEMU binary"));
>              return -1;
>          }
> +        *vhostfdSize = 0;
>          return 0;
>      }
>  
> @@ -441,23 +459,32 @@ qemuOpenVhostNet(virDomainDefPtr def,
>                                     "virtio network interfaces"));
>              return -1;
>          }
> +        *vhostfdSize = 0;
>          return 0;
>      }
>  
> -    *vhostfd = open("/dev/vhost-net", O_RDWR);
> -    virDomainAuditNetDevice(def, net, "/dev/vhost-net", *vhostfd >= 0);
> +    for (i = 0; i < *vhostfdSize; i++) {
> +        vhostfd[i] = open("/dev/vhost-net", O_RDWR);
> +        virDomainAuditNetDevice(def, net, "/dev/vhost-net", vhostfd[i] >= 0);
>  
> -    /* If the config says explicitly to use vhost and we couldn't open it,
> -     * report an error.
> -     */
> -    if ((*vhostfd < 0) &&
> -        (net->driver.virtio.name == VIR_DOMAIN_NET_BACKEND_TYPE_VHOST)) {
> -        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> -                       "%s", _("vhost-net was requested for an interface, "
> -                               "but is unavailable"));
> -        return -1;
> +        /* If the config says explicitly to use vhost and we couldn't open it,
> +         * report an error.
> +         */
> +        if (vhostfd[i] < 0 &&
> +            net->driver.virtio.name == VIR_DOMAIN_NET_BACKEND_TYPE_VHOST) {
> +            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> +                           "%s", _("vhost-net was requested for an interface, "
> +                                   "but is unavailable"));
> +            goto error;
> +        }
>      }
>      return 0;
> +
> +error:
> +    while (i--)
> +        VIR_FORCE_CLOSE(vhostfd[i]);
> +
> +    return -1;
>  }
>  
>  int
> @@ -6477,10 +6504,11 @@ qemuBuildInterfaceCommandLine(virCommandPtr cmd,
>          /* Attempt to use vhost-net mode for these types of
>             network device */
>          int vhostfd;
> +        int vhostfdSize = 1;
>  
> -        if (qemuOpenVhostNet(def, net, qemuCaps, &vhostfd) < 0)
> +        if (qemuOpenVhostNet(def, net, qemuCaps, &vhostfd, &vhostfdSize) < 0)
>              goto cleanup;
> -        if (vhostfd >= 0) {
> +        if (vhostfdSize > 0) {
>              virCommandTransferFD(cmd, vhostfd);
>              if (virAsprintf(&vhostfdName, "%d", vhostfd) < 0) {
>                  virReportOOMError();
> diff --git a/src/qemu/qemu_command.h b/src/qemu/qemu_command.h
> index 6765c3a..c87b754 100644
> --- a/src/qemu/qemu_command.h
> +++ b/src/qemu/qemu_command.h
> @@ -170,7 +170,8 @@ int qemuPhysIfaceConnect(virDomainDefPtr def,
>  int qemuOpenVhostNet(virDomainDefPtr def,
>                       virDomainNetDefPtr net,
>                       virQEMUCapsPtr qemuCaps,
> -                     int *vhostfd);
> +                     int *vhostfd,
> +                     int *vhostfdSize);
>  
>  int qemuNetworkPrepareDevices(virDomainDefPtr def);
>  
> diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
> index 0a1845a..fdc4b24 100644
> --- a/src/qemu/qemu_hotplug.c
> +++ b/src/qemu/qemu_hotplug.c
> @@ -689,6 +689,7 @@ int qemuDomainAttachNetDevice(virConnectPtr conn,
>      int tapfd = -1;
>      char *vhostfd_name = NULL;
>      int vhostfd = -1;
> +    int vhostfdSize = 0;
>      char *nicstr = NULL;
>      char *netstr = NULL;
>      virNetDevVPortProfilePtr vport = NULL;
> @@ -738,7 +739,8 @@ int qemuDomainAttachNetDevice(virConnectPtr conn,
>                                               priv->qemuCaps)) < 0)
>              goto cleanup;
>          iface_connected = true;
> -        if (qemuOpenVhostNet(vm->def, net, priv->qemuCaps, &vhostfd) < 0)
> +        vhostfdSize = 1;
> +        if (qemuOpenVhostNet(vm->def, net, priv->qemuCaps, &vhostfd, &vhostfdSize) < 0)
>              goto cleanup;
>      } else if (actualType == VIR_DOMAIN_NET_TYPE_DIRECT) {
>          if ((tapfd = qemuPhysIfaceConnect(vm->def, driver, net,
> @@ -746,10 +748,12 @@ int qemuDomainAttachNetDevice(virConnectPtr conn,
>                                            VIR_NETDEV_VPORT_PROFILE_OP_CREATE)) < 0)
>              goto cleanup;
>          iface_connected = true;
> -        if (qemuOpenVhostNet(vm->def, net, priv->qemuCaps, &vhostfd) < 0)
> +        vhostfdSize = 1;
> +        if (qemuOpenVhostNet(vm->def, net, priv->qemuCaps, &vhostfd, &vhostfdSize) < 0)
>              goto cleanup;
>      } else if (actualType == VIR_DOMAIN_NET_TYPE_ETHERNET) {
> -        if (qemuOpenVhostNet(vm->def, net, priv->qemuCaps, &vhostfd) < 0)
> +        vhostfdSize = 1;
> +        if (qemuOpenVhostNet(vm->def, net, priv->qemuCaps, &vhostfd, &vhostfdSize) < 0)
>              goto cleanup;
>      }
>  
> @@ -792,7 +796,7 @@ int qemuDomainAttachNetDevice(virConnectPtr conn,
>              goto no_memory;
>      }
>  
> -    if (vhostfd != -1) {
> +    if (vhostfdSize > 0) {
>          if (virAsprintf(&vhostfd_name, "vhostfd-%s", net->info.alias) < 0)
>              goto no_memory;
>      }

ACK.


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