Messages in this thread | | | Subject | Re: [PATCH] pci/sriov: Add an option to probe VFs or not before enabling SR-IOV | From | Bodong Wang <> | Date | Tue, 21 Mar 2017 08:43:32 -0500 |
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On 3/21/2017 1:01 AM, Alex Williamson wrote: > On Tue, 21 Mar 2017 16:43:05 +1100 > Gavin Shan <gwshan@linux.vnet.ibm.com> wrote: > >> On Mon, Mar 20, 2017 at 10:57:08PM -0600, Alex Williamson wrote: >>> On Mon, 20 Mar 2017 18:34:23 -0500 >>> Bodong Wang <bodong@mellanox.com> wrote: >> .../... >> >>>>> Bodong, I'm not sure if there is a requirement to load driver for the >>>>> specified number of VFs? That indicates no driver will be loaded for >>>>> other VFs. If so, this interface might serve the purpose as well. >>>> Gavin, thanks for the review. That is indeed an interesting suggestion. >>>> Theoretically, we can change that probe_vfs from boolean to integer. >>>> And use it as a counter to probe the first N VFs(if N < total_vfs). >>>> Let's see if there are any objections. >>> Is it just me or does this seem like a confusing user interface, ie. to >>> get binary on/off behavior a user now needs to 'cat total_vfs > >>> sriov_probe_vfs'. It's not very intuitive, what's the use case for it? >>> >> After it's changed to integer, it accepts number. If users want to load >> driver for all VFs and don't want to check the maximal number of VFs, >> they can simply write 0xffffffff. So "on" and "off" are replaced with 0xffffffff >> and 0, but users has to press the keyboard more times though. >> >> drivers/net/ethernet/mellanox/mlx4/main.c::probe_vfs_argc allows to specify >> the number of VFs with which we're going to bind drivers. Less time is needed >> to enable SRIOV capability. As I had in some development environment: assume >> PF supports 256 VFs and I'm going to enable all of them, but I only want to >> load driver for two of them, then test the data path on those two VFs. Besides, >> I can image the VF needn't a driver in host if it's going to be passed to guest. >> Not sure how much sense it makes. > Yes, I understand what you're trying to do, but I still think it's > confusing for a user interface. This also doesn't answer what's the > practical, typical user case you see where it's useful to probe some > VFs but not others. The case listed is a development case where you > could just as easily disable all probing, then manually bind the first > two VFs to the host driver. Which is the better design, impose a > confusing interface on all users to simplify an obscure development > environment or simplify the user interface and assume developers know > how to bind devices otherwise? Thanks, > > Alex
I agree with Alex on this concern. Sometimes, I need to probe 1 or 2 VFs to host side just for development purpose. Bind/unbind satisfy this case perfectly, and that's how current implementation is designed. But, from Gavin's use case, it will be a pain to bind/unbind hundreds of VFs. So, I want to understand how common this use case is. If it's not common, I prefer to keep current design because 1) the interface is much easier to understand and use 2) less error prone because no need to check current total_vfs and maintain a static counter to enable N vfs.
Bodong
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