Re: [PATCH] RDMA/siw,rxe: Make emulated devices virtual in the device tree

[Bart Van Assche <bvanassche@acm.org>]

On 11/6/20 6:00 AM, Jason Gunthorpe wrote:
> This moves siw and rxe to be virtual devices in the device tree:
> 
> lrwxrwxrwx 1 root root 0 Nov  6 13:55 /sys/class/infiniband/rxe0 -> ../../devices/virtual/infiniband/rxe0/
> 
> Previously they were trying to parent themselves to the physical device of
> their attached netdev, which doesn't make alot of sense.
> 
> My hope is this will solve some weird syzkaller hits related to sysfs as
> it could be possible that the parent of a netdev is another netdev, eg
> under bonding or some other syzkaller found netdev configuration.
> 
> Nesting a ib_device under anything but a physical device is going to cause
> inconsistencies in sysfs during destructions.

Hi Jason,

I do not know enough about the code touched by this patch to comment on
the patch itself. But I expect that the blktests code will have to be
modified to compensate for this change. How to translate the name of a
virtual RDMA device into a netdev device with this patch applied?

From the blktests project:

# Check whether or not an rdma_rxe instance has been associated with
# network interface $1.
has_rdma_rxe() {
	local f

	for f in /sys/class/infiniband/*/parent; do
		if [ -e "$f" ] && [ "$(<"$f")" = "$1" ]; then
			return 0
		fi
	done

	return 1
}

rdma_dev_to_net_dev() {
	local b d rdma_dev=$1

	b=/sys/class/infiniband/$rdma_dev/parent
	if [ -e "$b" ]; then
		echo "$(<"$b")"
	else
		echo "${rdma_dev%_siw}"
	fi
}

Bart.