> -----Original Message----- > From: Chris Wright [mailto:chrisw at redhat.com] > Sent: Friday, June 13, 2014 11:14 AM > To: Richardson, Bruce > Cc: Chris Wright; Stephen Hemminger; Thomas Monjalon; dev at dpdk.org > Subject: Re: [PATCH] igb_uio: cap max VFs at 7 to reserve one for PF > > * Richardson, Bruce (bruce.richardson at intel.com) wrote: > > > > > > > -----Original Message----- > > > From: Chris Wright [mailto:chrisw at redhat.com] > > > Sent: Friday, June 13, 2014 10:52 AM > > > To: Richardson, Bruce; Stephen Hemminger > > > Cc: Thomas Monjalon; dev at dpdk.org > > > Subject: [PATCH] igb_uio: cap max VFs at 7 to reserve one for PF > > > > > > To keep from confusing users, cap max VFs at 7, despite PCI SR-IOV config > > > space showing a max of 8. This reserves a queue pair for the PF. > > > > > > This issue was cited here: > > > > > > http://dpdk.org/ml/archives/dev/2014-April/001832.html > > > > > > Cc: Bruce Richardson <bruce.richardson at intel.com> > > > Cc: Stephen Hemminger <stephen at networkplumber.org> > > > Signed-off-by: Chris Wright <chrisw at redhat.com> > > > --- > > > > > > This is what Linux kernel driver does. I have only > > > compile tested it. Stephen sending to you and Bruce > > > in case you want to Ack and add to your current queue. > > > > > > > Sorry, NAK - at least for this implementation. > > Oh, that's fine. > > > Hardcoding this to 7 is a bad idea, as the actual max number of VFs > > supported > will depend on the actual hardware used. For someone using an 82599, they can > have up to 64 VFs, or 63+PF, so limiting so 7 in that case is a major > reduction in > capability. What might work there is querying the max number of VFs and > limiting to max - 1. > > But this is igb_uio, not 82599 (ixgbe).
igb_uio is used as the supporting kernel module for both the e1000/igb and ixgbe pmd implementations (as well as for the forthcoming i40e pmd). Despite the name, it's not just for igb-based NICs. > > > However, even with that, I would suggest that any limit should be possible > > to > override. It's entirely possible that someone max actually want to reserve the > full number of VFs, either because they don't want to use the NIC on the host > at > all, or because they are happy to use a VF on the host instead. Module > parameter to allow override might work - and information on it could be added > to the error message when we limit the VFs inside the driver. > > It's been a while since I've looked at this, but my recollection is > the PF must be there (basic mailbox handling, for example). > > Would you rather a simple warning message as a hint? I'm not sure about the PF still needing to be there or not - I'm not an expert in that area, so you may indeed be right. However, as for this patch, I'd probably be ok for now with a version that queried the max_vfs and limited based on that. If in future we do need to add an override it should be trivial to add later-on.
