Message-ID: <20120919085306.00006af9@unknown>
Date:	Wed, 19 Sep 2012 08:53:06 -0700
From:	Greg Rose <gregory.v.rose@...el.com>
To:	Yuval Mintz <yuvalmin@...adcom.com>
CC:	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Ariel Elior <ariele@...adcom.com>,
	Eilon Greenstein <eilong@...adcom.com>
Subject: Re: New commands to configure IOV features

On Wed, 19 Sep 2012 14:07:19 +0300
Yuval Mintz <yuvalmin@...adcom.com> wrote:

> >>> Back to the original discussion though--has anyone got any ideas
> >>> about the best way to trigger runtime creation of VFs?  I don't
> >>> know what the binary APIs looks like, but via sysfs I could see
> >>> something like
> >>>
> >>> echo number_of_new_vfs_to_create >
> >>> /sys/bus/pci/devices/<address>/create_vfs
> >>>
> >>> Something else that occurred to me--is there buy-in from driver
> >>> maintainers?  I know the Intel ethernet drivers (what I'm most
> >>> familiar
> >>> with) would need to be substantially modified to support
> >>> on-the-fly addition of new vfs.  Currently they assume that the
> >>> number of vfs is known at module init time.
> >>
> >> Why couldn't rtnl_link_ops be used for this. It is already the
> >> preferred interface to create vlan's, bond devices, and other
> >> virtual devices? The one issue is that do the created VF's exist
> >> in kernel as devices or only visible to guest?
> > 
> > I would say that rtnl_link_ops are network oriented and not
> > appropriate for something like a storage controller or graphics
> > device, which are two other common SR-IOV capable devices.
> 
> Hi Dave,
> 
> We're currently fine-tuning our SRIOV support, which we will shortly
> send upstream.
> 
> We've encountered a problem though - all drivers currently supporting
> SRIOV do so with the usage of a module param: e.g., 'max_vfs' for
> ixgbe, 'num_vfs' for benet, etc.
> The SRIOV feature is disabled by default on all the drivers; it can
> only be enabled via usage of the module param.
> 
> We don't want the lack of SRIOV module param in the bnx2x driver to be
> the bottle-neck when we'll submit the SRIOV feature upstream, and we
> also don't want to enable SRIOV by default (following the same logic
> of other drivers; most users don't use SRIOV and it would strain their
> resources).
> 
> As we see it, there are several possible ways of solving the issue:
>  1. Use some network-tool (e.g., ethtool).
>  2. Implement a standard sysfs interface for PCIe devices, as SRIOV is
>     not solely network-related (this should be done via the PCI linux
>     tree).

I was not able to attend the Linux conference held at the end of August
myself but coworkers of mine here at Intel informed that method 2 here
seems to be the preferred approach.  Perhaps some folks who attended
the the conference can chime in with more specifics.

- Greg
LAN Access Division
Intel Corp.



>  3. Implement a module param in our bnx2x code.
> 
> We would like to know what's your preferred method for solving this
> issue, and to hear if you have another (better?) method by which we
> can add this kind of support.
> 
> Thanks,
> Yuval Mintz
> 
> 
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