On Fri, Aug 18, 2017 at 12:07:45PM -0400, Doug Ledford wrote: > On Fri, 2017-08-18 at 18:58 +0300, Leon Romanovsky wrote: > > On Fri, Aug 18, 2017 at 11:00:04AM -0400, Doug Ledford wrote: > > > On Wed, 2017-06-28 at 10:23 +0000, Elior, Ariel wrote: > > > > > From: Leon Romanovsky [mailto:leon@xxxxxxxxxx] > > > > > Sent: Wednesday, June 28, 2017 1:11 PM > > > > > To: Amrani, Ram <Ram.Amrani@xxxxxxxxxx> > > > > > Cc: dledford@xxxxxxxxxx; linux-rdma@xxxxxxxxxxxxxxx; Elior, > > > > > Ariel > > > > > <Ariel.Elior@xxxxxxxxxx> > > > > > Subject: Re: [PATCH rdma v1 1/1] IB/core: Fix input len in > > > > > multiple > > > > > user verbs > > > > > > > > > > On Wed, Jun 28, 2017 at 10:02:45AM +0000, Amrani, Ram wrote: > > > > > > > > Most user verbs pass user data to the kernel with the > > > > > > > > inclusion of the > > > > > > > > ib_uverbs_cmd_hdr structure. This is problematic because > > > > > > > > the > > > > > > > > vendor has > > > > > > > > no ideas if the verb was called by a legacy verb or an > > > > > > > > extended verb. > > > > > > > > > > > > > > Why vendor should know about it? It has midlayer (ib/core) > > > > > > > between him > > > > > > > and user to handle it. > > > > > > > > > > > > > > > > > > > Knowing the inlen can be used to determine if the library is > > > > > > newer than > > > > > > the kernel and what features it supports or not. > > > > > > > > > > It is not interesting case, because we are not breaking UAPI, > > > > > only > > > > > extending. It ensures that kernel will fill as much as possible > > > > > and > > > > > will > > > > > always have success in it. After that it is library > > > > > responsibility > > > > > to > > > > > understand if everything was filled. > > > > > > > > > > Thanks > > > > > > > > In our case, kernel driver needs to know whether library supports > > > > a > > > > certain > > > > feature (doorbell overflow recovery). It doesn't care if it was > > > > an > > > > extended > > > > verb or not, but it cares whether the lib is sufficiently new to > > > > have > > > > provided > > > > the required information. If the library is sufficiently new > > > > (supports) then > > > > kernel will register the library's doorbell address with the > > > > overflow > > > > recovery > > > > mechanism, and perform recovery if required, otherwise it would > > > > not > > > > (as the > > > > library is not supplying the necessary information for recovery > > > > to > > > > take place). > > > > This is not something the library needs to know, but the kernel > > > > driver. Having > > > > correct input len is required for successfully avoiding breaking > > > > the > > > > UAPI. > > > > > > Leon, does this explanation resolve your objections? Also, have > > > you > > > checked the mlx5/mthca portions of this patch? > > > > Yes, let's me recheck/rerun the patch and post results. > > If for any reasons you don't hear from me till Wednesday, take it. > > > > Thanks > > Works for me, thanks. The series worked for us and we didn't encounter unknown failures. Thanks > > -- > Doug Ledford <dledford@xxxxxxxxxx> > GPG KeyID: B826A3330E572FDD > Key fingerprint = AE6B 1BDA 122B 23B4 265B 1274 B826 A333 0E57 2FDD >
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