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Re: [libvirt] [PATCH v2 1/4] util: fixing wrong assumption that PF has to have netdev assigned



On 11/17/18 8:51 PM, Radoslaw Biernacki wrote:
> libvirt wrongly assumes that VF netdev has to have the
> netdev assigned to PF. There is no such requirement in SRIOV standard.
> This patch change the virNetDevSwitchdevFeature() function to deal
> with SRIOV devices which does not have netdev on PF. Also removes
> one comment about PF netdev assumption.
> The error report was moved outside from virNetDevGetPhysicalFunction()
> and the error message changed slightly to reflect other potential
> root causes of error.
> 
> One example of such devices is ThunderX VNIC.
> By applying this change, VF device is used for virNetlinkCommand() as
> it is the only netdev assigned to VNIC.
> 
> Signed-off-by: Radoslaw Biernacki <radoslaw biernacki linaro org>
> ---
>  src/util/virnetdev.c | 22 ++++++++++----------
>  1 file changed, 11 insertions(+), 11 deletions(-)
> 
> diff --git a/src/util/virnetdev.c b/src/util/virnetdev.c
> index 5867977df4..f1c2ba8c17 100644
> --- a/src/util/virnetdev.c
> +++ b/src/util/virnetdev.c
> @@ -1358,15 +1358,8 @@ virNetDevGetPhysicalFunction(const char *ifname, char **pfname)
>          goto cleanup;
>      }
>  
> -    if (!*pfname) {
> -        /* this shouldn't be possible. A VF can't exist unless its
> -         * PF device is bound to a network driver
> -         */
> -        virReportError(VIR_ERR_INTERNAL_ERROR,
> -                       _("The PF device for VF %s has no network device name"),
> -                       ifname);

If you remove this error reporting you have to make sure that all the
callers do report it (if needed).

Worse, this function has a non-Linux stub which sets errno = ENOSYS and
reports an error. Therefore I think the right solution is to keep this
error in and ..

> +    if (!*pfname)
>          goto cleanup;
> -    }
>  
>      ret = 0;
>   cleanup:
> @@ -1453,8 +1446,12 @@ virNetDevGetVirtualFunctionInfo(const char *vfname, char **pfname,
>  
>      *pfname = NULL;
>  
> -    if (virNetDevGetPhysicalFunction(vfname, pfname) < 0)
> +    if (virNetDevGetPhysicalFunction(vfname, pfname) < 0) {
> +        virReportError(VIR_ERR_INTERNAL_ERROR,
> +                       _("Cannot get PF netdev name for VF %s"),
> +                       vfname);
>          return ret;
> +    }
>  
>      if (virNetDevSysfsFile(&pf_sysfs_path, *pfname, "device") < 0)
>          goto cleanup;
> @@ -3182,8 +3179,11 @@ virNetDevSwitchdevFeature(const char *ifname,
>      if ((is_vf = virNetDevIsVirtualFunction(ifname)) < 0)
>          return ret;
>  
> -    if (is_vf == 1 && virNetDevGetPhysicalFunction(ifname, &pfname) < 0)
> -        goto cleanup;
> +    if (is_vf == 1) {
> +        /* ignore error if PF does noto have netdev assigned
> +         * in that case pfname == NULL */
> +        ignore_value(virNetDevGetPhysicalFunction(ifname, &pfname));

.. just call this function like this:

  if (virNetDevGetPhysicalFunction(ifname, &pfname) < 0) {
    /* Ignore error if PF does not have a netdev assigned
     * in which case pfname == NULL. */
    virResetLastError();
  }


Sorry for not realizing this in v1.

Michal


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