Re: [PATCH rdma-next v1 3/3] RDMA: Fix link active_speed size

From: Leon Romanovsky <leon@kernel.org>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Doug Ledford <dledford@redhat.com>,
	Aharon Landau <aharonl@mellanox.com>,
	Adit Ranadive <aditr@vmware.com>,
	Ariel Elior <aelior@marvell.com>,
	Dennis Dalessandro <dennis.dalessandro@intel.com>,
	Devesh Sharma <devesh.sharma@broadcom.com>,
	linux-rdma@vger.kernel.org,
	Michael Guralnik <michaelgur@nvidia.com>,
	Michal Kalderon <mkalderon@marvell.com>,
	Mike Marciniszyn <mike.marciniszyn@intel.com>,
	Naresh Kumar PBS <nareshkumar.pbs@broadcom.com>,
	Selvin Xavier <selvin.xavier@broadcom.com>,
	Somnath Kotur <somnath.kotur@broadcom.com>,
	Sriharsha Basavapatna <sriharsha.basavapatna@broadcom.com>,
	VMware PV-Drivers <pv-drivers@vmware.com>
Subject: Re: [PATCH rdma-next v1 3/3] RDMA: Fix link active_speed size
Date: Tue, 8 Sep 2020 18:04:27 +0300	[thread overview]
Message-ID: <20200908150427.GG421756@unreal> (raw)
In-Reply-To: <20200908144646.GJ9166@nvidia.com>

On Tue, Sep 08, 2020 at 11:46:46AM -0300, Jason Gunthorpe wrote:
> On Tue, Sep 08, 2020 at 05:42:05PM +0300, Leon Romanovsky wrote:
> > On Tue, Sep 08, 2020 at 11:27:56AM -0300, Jason Gunthorpe wrote:
> > > On Tue, Sep 08, 2020 at 05:26:51PM +0300, Leon Romanovsky wrote:
> > > > On Tue, Sep 08, 2020 at 11:19:24AM -0300, Jason Gunthorpe wrote:
> > > > > On Wed, Sep 02, 2020 at 10:45:03AM +0300, Leon Romanovsky wrote:
> > > > > > From: Aharon Landau <aharonl@mellanox.com>
> > > > > >
> > > > > > According to the IB spec active_speed size should be u16 and not u8 as
> > > > > > before. Changing it to allow further extensions in offered speeds.
> > > > > >
> > > > > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> > > > > > Signed-off-by: Aharon Landau <aharonl@mellanox.com>
> > > > > > Reviewed-by: Michael Guralnik <michaelgur@nvidia.com>
> > > > > > Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
> > > > > >  drivers/infiniband/core/uverbs_std_types_device.c | 3 ++-
> > > > > >  drivers/infiniband/core/verbs.c                   | 2 +-
> > > > > >  drivers/infiniband/hw/bnxt_re/bnxt_re.h           | 2 +-
> > > > > >  drivers/infiniband/hw/hfi1/verbs.c                | 2 +-
> > > > > >  drivers/infiniband/hw/mlx5/main.c                 | 8 ++------
> > > > > >  drivers/infiniband/hw/ocrdma/ocrdma_verbs.c       | 2 +-
> > > > > >  drivers/infiniband/hw/qedr/verbs.c                | 2 +-
> > > > > >  drivers/infiniband/hw/qib/qib.h                   | 6 +++---
> > > > > >  drivers/infiniband/hw/vmw_pvrdma/pvrdma_verbs.h   | 2 +-
> > > > > >  include/rdma/ib_verbs.h                           | 4 ++--
> > > > > >  10 files changed, 15 insertions(+), 18 deletions(-)
> > > > > >
> > > > > > diff --git a/drivers/infiniband/core/uverbs_std_types_device.c b/drivers/infiniband/core/uverbs_std_types_device.c
> > > > > > index 75df2094a010..7b03446b6936 100644
> > > > > > +++ b/drivers/infiniband/core/uverbs_std_types_device.c
> > > > > > @@ -165,7 +165,8 @@ void copy_port_attr_to_resp(struct ib_port_attr *attr,
> > > > > >  	resp->subnet_timeout = attr->subnet_timeout;
> > > > > >  	resp->init_type_reply = attr->init_type_reply;
> > > > > >  	resp->active_width = attr->active_width;
> > > > > > -	resp->active_speed = attr->active_speed;
> > > > > > +	WARN_ON(attr->active_speed & ~0xFF);
> > > > >
> > > > > ?? This doesn't seem like a warn on situation..
> > > >
> > > > Why? We are returning u8 to the user, so need to catch overflow.
> > >
> > > We need to have actual backwards compat here, not just throw a warning
> > > at the syscall boundary
> >
> > We don't have fallback and don't have speed that crosses u8 limit yet.
> > This WARN_ON() is needed to ensure that we properly extend
> > ib_port_speed.
>
> Until we have some compat story I don't want to just increase this
> value, it clearly renders the device unusable, so why do it?

Because IBTA port speed extension was already approved, it is just
not published yet.

I need to prepare code as much as possible.

Thanks

>
> Jason