Re: [PATCH rdma-next 4/4] RDMA/uverbs: Expose the new GID query API to user space

[Jason Gunthorpe <jgg@nvidia.com>]

On Sun, Sep 13, 2020 at 12:13:02PM +0300, Leon Romanovsky wrote:
> > > +static int UVERBS_HANDLER(UVERBS_METHOD_QUERY_GID_ENTRY)(
> > > +	struct uverbs_attr_bundle *attrs)
> > > +{
> > > +	const struct ib_gid_attr *gid_attr;
> > > +	struct ib_uverbs_gid_entry entry;
> > > +	struct ib_ucontext *ucontext;
> > > +	struct ib_device *ib_dev;
> > > +	u32 gid_index;
> > > +	u32 port_num;
> > > +	u32 flags;
> > > +	int ret;
> > > +
> > > +	ret = uverbs_get_flags32(&flags, attrs,
> > > +				 UVERBS_ATTR_QUERY_GID_ENTRY_FLAGS, 0);
> > > +	if (ret)
> > > +		return ret;
> > > +
> > > +	ret = uverbs_get_const(&port_num, attrs,
> > > +			       UVERBS_ATTR_QUERY_GID_ENTRY_PORT);
> > > +	if (ret)
> > > +		return ret;
> > > +
> > > +	ret = uverbs_get_const(&gid_index, attrs,
> > > +			       UVERBS_ATTR_QUERY_GID_ENTRY_GID_INDEX);
> > > +	if (ret)
> > > +		return ret;
> > > +
> > > +	ucontext = ib_uverbs_get_ucontext(attrs);
> > > +	if (IS_ERR(ucontext))
> > > +		return PTR_ERR(ucontext);
> > > +	ib_dev = ucontext->device;
> >
> > > +	if (!rdma_is_port_valid(ib_dev, port_num))
> > > +		return -EINVAL;
> > > +
> > > +	if (!rdma_ib_or_roce(ib_dev, port_num))
> > > +		return -EINVAL;
> >
> > Why these two tests? I would expect rdma_get_gid_attr() to do them
> 
> First check is not needed, but the second check doesn't exist in
> rdma_get_gid_attr(). We don't check that table returned from
> rdma_gid_table() call exists.

Oh that is a bit exciting, maybe it should be checked...

Ideally we should also block this uapi entirely if the device doesn't
have a gid table, so this should be -EOPNOTSUP and moved up to the
top so it can be moved once we figure it out.

> > > +	gid_attr = rdma_get_gid_attr(ib_dev, port_num, gid_index);
> > > +	if (IS_ERR(gid_attr))
> > > +		return PTR_ERR(gid_attr);
> > > +
> > > +	memcpy(&entry.gid, &gid_attr->gid, sizeof(gid_attr->gid));
> > > +	entry.gid_index = gid_attr->index;
> > > +	entry.port_num = gid_attr->port_num;
> > > +	entry.gid_type = gid_attr->gid_type;
> > > +	ret = rdma_get_ndev_ifindex(gid_attr, &entry.netdev_ifindex);
> >
> > Use rdma_read_gid_attr_ndev_rcu()
> 
> I don't want to bring below logic to uverbs* file.
> 
>   1263         if (rdma_protocol_ib(gid_attr->device, gid_attr->port_num)) {
>   1264                 *ndev_ifindex = 0;
>   1265                 return 0;
>   1266         }

Shouldn't be needed, rdma_read_gid_attr_ndev_rcu() already returns -1
for IB

Jason