Re: [PATCH rdma-next v2 0/9] Restore failure of destroy commands

[Leon Romanovsky <leon@kernel.org>]

On Wed, Sep 09, 2020 at 03:06:07PM -0300, Jason Gunthorpe wrote:
> On Mon, Sep 07, 2020 at 03:09:12PM +0300, Leon Romanovsky wrote:
> > From: Leon Romanovsky <leonro@nvidia.com>
> >
> > Changelog:
> > v2:
> >  * Rebased on top of the 524d8ffd07f0
> >  * Removed "udata" check in destroy flows
> >  * Changed ib_free_cq to return early
> >  * Used Jason's suggestion to implement "RDMA/mlx5: Issue FW command to destroy
> >    SRQ on reentry" patch.
> > v1
> >  * Changed returned value in efa_destroy_ah() from EINVAL to EOPNOTSUPP
> >  * https://lore.kernel.org/lkml/20200830084010.102381-1-leon@kernel.org
> > v0:
> >  * https://lore.kernel.org/lkml/20200824103247.1088464-1-leon@kernel.org
> >
> > Hi,
> >
> > This series restores the ability to fail on destroy commands, due to the
> > fact that mlx5_ib DEVX implementation interleaved ib_core objects
> > with FW objects without sharing reference counters.
> >
> > In retrospect, every part of the mlx5_ib flow is correct.
> >
> > It started from IBTA which was written by HW engineers with HW in mind and
> > they allowed to fail in destruction. FW implemented it with symmetrical
> > interface like any other command and propagated error back to the kernel,
> > which forwarded it to the libibverbs and kernel ULPs.
> >
> > Libibverbs was designed with IBTA spec in hand putting destroy errors in
> > stone. Up till mlx5_ib DEVX, it worked well, because the IB verbs objects
> > are counted by the kernel and ib_core ensures that FW destroy will success
> > by managing various reference counters on such objects.
> >
> > The extension of the mlx5 driver changed this flow when allowed DEVX objects
> > that are not managed by ib_core to be interleaved with the ones under ib_core
> > responsibility.
> >
> > The drivers that want to implement DEVX flows must ensure that FW/HW
> > destroys are performed as early as possible before any other internal
> > cleanup. After HW destroys, drivers are not allowed to fail.
> >
> > This series includes two patches (WQ and "potential race") that will
> > require extra work in mlx5_ib, they both theoretical. WQ is not in use
> > in DEVX, but is needed to make interface symmetrical to other objects.
> > "Potential race" is in ULP flow that ensures that SRQ is destroyed in
> > proper order.
> >
> > Thanks
> >
> > Leon Romanovsky (9):
> >   RDMA: Restore ability to fail on PD deallocate
> >   RDMA: Restore ability to fail on AH destroy
> >   RDMA/mlx5: Issue FW command to destroy SRQ on reentry
> >   RDMA: Restore ability to fail on SRQ destroy
> >   RDMA/core: Delete function indirection for alloc/free kernel CQ
> >   RDMA: Allow fail of destroy CQ
> >   RDMA: Change XRCD destroy return value
> >   RDMA: Restore ability to return error for destroy WQ
> >   RDMA: Make counters destroy symmetrical
>
> Thanks, applied to for-next with the changes I noted:

Thanks for taking care. LGTM.