From: Eric Farman farman@linux.ibm.com
[ Upstream commit ff598081e5b9d0bdd6874bfe340811bbb75b35e4 ]
The pointer to mdev_bus_compat_class is statically defined at the top of mdev_core, and was originally (commit 7b96953bc640 ("vfio: Mediated device Core driver") serialized by the parent_list_lock. The blamed commit removed this mutex, leaving the pointer initialization unserialized. As a result, the creation of multiple MDEVs in parallel (such as during boot) can encounter errors during the creation of the sysfs entries, such as:
[ 8.337509] sysfs: cannot create duplicate filename '/class/mdev_bus' [ 8.337514] vfio_ccw 0.0.01d8: MDEV: Registered [ 8.337516] CPU: 13 PID: 946 Comm: driverctl Not tainted 6.4.0-rc7 #20 [ 8.337522] Hardware name: IBM 3906 M05 780 (LPAR) [ 8.337525] Call Trace: [ 8.337528] [<0000000162b0145a>] dump_stack_lvl+0x62/0x80 [ 8.337540] [<00000001622aeb30>] sysfs_warn_dup+0x78/0x88 [ 8.337549] [<00000001622aeca6>] sysfs_create_dir_ns+0xe6/0xf8 [ 8.337552] [<0000000162b04504>] kobject_add_internal+0xf4/0x340 [ 8.337557] [<0000000162b04d48>] kobject_add+0x78/0xd0 [ 8.337561] [<0000000162b04e0a>] kobject_create_and_add+0x6a/0xb8 [ 8.337565] [<00000001627a110e>] class_compat_register+0x5e/0x90 [ 8.337572] [<000003ff7fd815da>] mdev_register_parent+0x102/0x130 [mdev] [ 8.337581] [<000003ff7fdc7f2c>] vfio_ccw_sch_probe+0xe4/0x178 [vfio_ccw] [ 8.337588] [<0000000162a7833c>] css_probe+0x44/0x80 [ 8.337599] [<000000016279f4da>] really_probe+0xd2/0x460 [ 8.337603] [<000000016279fa08>] driver_probe_device+0x40/0xf0 [ 8.337606] [<000000016279fb78>] __device_attach_driver+0xc0/0x140 [ 8.337610] [<000000016279cbe0>] bus_for_each_drv+0x90/0xd8 [ 8.337618] [<00000001627a00b0>] __device_attach+0x110/0x190 [ 8.337621] [<000000016279c7c8>] bus_rescan_devices_helper+0x60/0xb0 [ 8.337626] [<000000016279cd48>] drivers_probe_store+0x48/0x80 [ 8.337632] [<00000001622ac9b0>] kernfs_fop_write_iter+0x138/0x1f0 [ 8.337635] [<00000001621e5e14>] vfs_write+0x1ac/0x2f8 [ 8.337645] [<00000001621e61d8>] ksys_write+0x70/0x100 [ 8.337650] [<0000000162b2bdc4>] __do_syscall+0x1d4/0x200 [ 8.337656] [<0000000162b3c828>] system_call+0x70/0x98 [ 8.337664] kobject: kobject_add_internal failed for mdev_bus with -EEXIST, don't try to register things with the same name in the same directory. [ 8.337668] kobject: kobject_create_and_add: kobject_add error: -17 [ 8.337674] vfio_ccw: probe of 0.0.01d9 failed with error -12 [ 8.342941] vfio_ccw_mdev aeb9ca91-10c6-42bc-a168-320023570aea: Adding to iommu group 2
Move the initialization of the mdev_bus_compat_class pointer to the init path, to match the cleanup in module exit. This way the code in mdev_register_parent() can simply link the new parent to it, rather than determining whether initialization is required first.
Fixes: 89345d5177aa ("vfio/mdev: embedd struct mdev_parent in the parent data structure") Reported-by: Alexander Egorenkov egorenar@linux.ibm.com Signed-off-by: Eric Farman farman@linux.ibm.com Reviewed-by: Kevin Tian kevin.tian@intel.com Reviewed-by: Christoph Hellwig hch@lst.de Reviewed-by: Tony Krowiak akrowiak@linux.ibm.com Reviewed-by: Jason Gunthorpe jgg@nvidia.com Link: https://lore.kernel.org/r/20230626133642.2939168-1-farman@linux.ibm.com Signed-off-by: Alex Williamson alex.williamson@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/vfio/mdev/mdev_core.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-)
diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c index 58f91b3bd670c..ed4737de45289 100644 --- a/drivers/vfio/mdev/mdev_core.c +++ b/drivers/vfio/mdev/mdev_core.c @@ -72,12 +72,6 @@ int mdev_register_parent(struct mdev_parent *parent, struct device *dev, parent->nr_types = nr_types; atomic_set(&parent->available_instances, mdev_driver->max_instances);
- if (!mdev_bus_compat_class) { - mdev_bus_compat_class = class_compat_register("mdev_bus"); - if (!mdev_bus_compat_class) - return -ENOMEM; - } - ret = parent_create_sysfs_files(parent); if (ret) return ret; @@ -251,13 +245,24 @@ int mdev_device_remove(struct mdev_device *mdev)
static int __init mdev_init(void) { - return bus_register(&mdev_bus_type); + int ret; + + ret = bus_register(&mdev_bus_type); + if (ret) + return ret; + + mdev_bus_compat_class = class_compat_register("mdev_bus"); + if (!mdev_bus_compat_class) { + bus_unregister(&mdev_bus_type); + return -ENOMEM; + } + + return 0; }
static void __exit mdev_exit(void) { - if (mdev_bus_compat_class) - class_compat_unregister(mdev_bus_compat_class); + class_compat_unregister(mdev_bus_compat_class); bus_unregister(&mdev_bus_type); }