> >> On Fri, Oct 20, 2017 at 10:10 AM, Jiri Pirko <j...@resnulli.us> wrote: > >> > Fri, Oct 20, 2017 at 04:03:55PM CEST, steven.l...@broadcom.com wrote: > >> >>On Thu, Oct 19, 2017 at 5:39 PM, Jiri Pirko <j...@resnulli.us> wrote: > >> >>> Thu, Oct 19, 2017 at 10:32:21PM CEST, yuv...@mellanox.com wrote: > >> >>>>> Adding DEVLINK_PERM_CONFIG_MSIX_VECTORS_PER_VF > >> permanent > >> >>>>> config > >> >>>>> parameter. Defines number of MSI-X vectors allocated per VF. > >> >>>>> Value is permanent (stored in NVRAM), so becomes the new > default > >> >>>>> value for this device. > >> >>>> > >> >>>>Sounds like you're having this enforce the same configuration for all > >> child VFs. > >> >>> > >> >>> Yeah, this sounds like per-port config. > >> >>> > >> >> > >> >>Well, it gets a little tricky here. I assume some cards handle this > >> >>per-port. Other cards might handle this per PF, where PF may not > >> >>always correspond 1:1 with a port. And some cards maybe just allow a > >> >>single value for this parameter for the entire card, covering all > >> >>ports/PFs. > >> >> > >> >>To keep things simple and as general as possible, it made sense to set > >> >>all parameters on a per-PCI device level. As I mentioned in my > >> >>cover-letter, the devices most likely to use these proposed commands > >> >>do not have a single "whole asic" PCI b/d/f with internal mechanism > >> >>for accessing ports - most expose each port (and each function on each > >> >>port) as a separate PCI b/d/f, with no separate "whole asic" PCI > >> >>b/d/f. That's how the BCM cards work, and I think that's how the > MLNX > >> >>cards work, and others that would be likely to use these cmds. > >> >> > >> >>So, to summarize, you direct the command to the PCI b/d/f you want > to > >> >>target. Does this make sense? > >> > > >> > So you plan to have 1 devlink instance for each vf? Not sure that > >> > does sound right to me :/ > >> > > >> > >> For the commands proposed in this patchset, AFAIK they all apply on a > >> per-PF or broader, i.e. per-port or whole-card, granularity, since > >> they affect permanent config that applies at boot-up. So, no, the VFs > >> don't really come into play here. > > > > Regardless of whether you're planning on having VFs as devlink instances, > > the actual attribute question remains - > > you're proposing an attribute that forces all VFs to have the same value. > > This probably suits your PCI core limitations but other vendors might have > > a different capability set, and accepting this design limitation now would > > muck all future extension attempts of such attributes. > > > > I think VF configurations should be planned in advance for supporting a > > per-VF Configuration whenever it's possible - even if not required > [/possible] > > by the one pushing the new attribute. > > > > The commands being added in this patch are for permanent (i.e. NVRAM) > config - essentially setting the new default values for various > features of the device at boot-up. At that initialization time, no > VFs are yet instantiated. > > So my perspective was, in general (not just for our specific device / > design), it doesn't seem like permanent config parameters would be set > on individual VFs. That was what my previous comment was trying to > convey.
That's an odd assumption; Why should you assume there's some device that allows configuring persistent behavior for all VFs but think no other would set the same on a per-VF basis? > If that assumption is wrong, though, and there is some device that has > NVRAM config that is set per-VF, I assume the user would instantiate > the VF and then call the devlink API on the pci device corresponding > to the VF they with to affect, and I think the model proposed still > works. What would be the purpose of re-configuring a value reflected in the PCI device for an already instantiated VF? > Are you suggesting adding a mechanism to set NVRAM parameters on a > per-VF basis, without instantiating the VF first? I would prefer not > adding such a mechanism unless/until there's a use case for it. The thing is that you're suggesting a new UAPI; We don't have the leisure of pushing a partial implementation and changing it later on.
