On Monday 05 December 2011 23:26, Ben Hutchings wrote:
> The 'probe_vf' parameter is very odd. Why do you think it is necessary
> to make this a module parameter? It should be possible to bind and
> unbind the driver from each VF dynamically via sysfs but this parameter
> appears to restrict that.
>
The host which sees the PF will also see all the VFs once they come up.
As each VF appears (as seen by 'lspci'), the O/S will invoke the "probe"
method for that VF. Without the "probe_vf" parameter, this probe would
result in all the VFs being bound to the PF host (and thus unavailable for
guests).
The small section of code which makes use of the probe_vf parameter
(file net/ethernet/mellanox/mlx4_main.c):
/* Detect if this device is a virtual function */
if (id && id->driver_data & MLX4_VF) {
/* When acting as pf, we normally skip vfs unless explicitly
* requested to probe them. */
if (sr_iov && extended_func_num(pdev) > probe_vf) {
mlx4_warn(dev, "Skipping virtual function:%d\n",
extended_func_num(pdev));
err = -ENODEV;
goto err_free_dev;
}
If you invoke "dmesg" on the PF host, you will see a series of the
"Skipping... " messages, one per VF. If probe_vf > 0, the PF-host will
reserve some VFs for its own use, and not issue the "Skipping..." message
for those VFs.
-Jack
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