netdev - RE: New commands to configure IOV features

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Date:	Thu, 20 Sep 2012 15:39:08 +0000
From:	"Rose, Gregory V" <gregory.v.rose@...el.com>
To:	Ben Hutchings <bhutchings@...arflare.com>,
	Yinghai Lu <yinghai@...nel.org>
CC:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Yuval Mintz <yuvalmin@...adcom.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Ariel Elior <ariele@...adcom.com>,
	Eilon Greenstein <eilong@...adcom.com>,
	linux-pci <linux-pci@...r.kernel.org>
Subject: RE: New commands to configure IOV features

> -----Original Message-----
> From: Ben Hutchings [mailto:bhutchings@...arflare.com]
> Sent: Wednesday, September 19, 2012 6:23 PM
> To: Yinghai Lu
> Cc: Bjorn Helgaas; Rose, Gregory V; Yuval Mintz; davem@...emloft.net;
> netdev@...r.kernel.org; Ariel Elior; Eilon Greenstein; linux-pci
> Subject: Re: New commands to configure IOV features
> 
> On Wed, 2012-09-19 at 17:19 -0700, Yinghai Lu wrote:
> > On Wed, Sep 19, 2012 at 3:46 PM, Ben Hutchings
> > <bhutchings@...arflare.com> wrote:
> > > On Wed, 2012-09-19 at 15:17 -0700, Yinghai Lu wrote:
> > >> +max_vfs_store(struct device *dev, struct device_attribute *attr,
> > >> +                const char *buf, size_t count) {
> > >> +       unsigned long val;
> > >> +       struct pci_dev *pdev = to_pci_dev(dev);
> > >> +
> > >> +       if (strict_strtoul(buf, 0, &val) < 0)
> > >> +               return -EINVAL;
> > >> +
> > >> +       pdev->max_vfs = val;
> > >> +
> > >> +       return count;
> > >> +}
> > > [...]
> > >
> > > Then what would actually trigger creation of the VFs?  There's no
> > > way we can assume that some sysfs attribute will be written before
> > > the PF driver is loaded (what if it's built-in?).  I thought the
> > > idea was to add a driver callback that would be called when the
> > > sysfs attribute was written.
> >
> > could just stop the device and add it back again?
> 
> This is highly disruptive and I think it would be totally unacceptable for
> at least networking devices.

Agreed.

We need the driver callback.

- Greg