On regular bootup, devices get registered to vmbus first, so when
uio_hv_generic driver for a particular device type is probed,
the device is already initialized and added, so sysfs creation in
uio_hv_generic probe works fine. However, when device is removed
and brought back, the channel rescinds and again gets registered
to vmbus. However this time, the uio_hv_generic driver is already
registered to probe for that device and in this case sysfs creation
is tried before the device gets initialized completely. Fix this by
deferring sysfs creation till device gets initialized completely.
Problem path:
vmbus_device_register
device_register
uio_hv_generic probe
sysfs_create_bin_file (fails here)
kset_create_and_add (dependency)
vmbus_add_channel_kobj (dependency)
Fixes: 9ab877a6ccf8 ("uio_hv_generic: make ring buffer attribute for primary channel")
Cc: stable@xxxxxxxxxx
Co-developed-by: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Naman Jain <namjain@xxxxxxxxxxxxxxxxxxx>
---
DPDK use-case depend on this sysfs node so to maintain backward compatibility and not break
DPDK, we could not remove sysfs logic from uio_hv_generic probe.
https://github.com/DPDK/dpdk/blob/main/drivers/bus/vmbus/linux/vmbus_uio.c#L360
Tried reordering functions in vmbus_device_register and also finding alternate functions
for device initialization, but could not find any other viable solution.
Explored the use of ATTRIBUTE_GROUPS and DEVICE_ATTR_RW but with that, I could create sysfs
node for a particular device but not for the channel for that device, as we need to.
