diff options
| author | Lu Baolu <baolu.lu@linux.intel.com> | 2025-02-28 18:27:26 +0800 |
|---|---|---|
| committer | Joerg Roedel <jroedel@suse.de> | 2025-02-28 12:19:01 +0100 |
| commit | b150654f74bf0df8e6a7936d5ec51400d9ec06d8 (patch) | |
| tree | 48e1d3ec86d80adb90dfca369e25987b64d31fc4 | |
| parent | 64f792981e35e191eb619f6f2fefab76cc7d6112 (diff) | |
iommu/vt-d: Fix suspicious RCU usage
Commit <d74169ceb0d2> ("iommu/vt-d: Allocate DMAR fault interrupts
locally") moved the call to enable_drhd_fault_handling() to a code
path that does not hold any lock while traversing the drhd list. Fix
it by ensuring the dmar_global_lock lock is held when traversing the
drhd list.
Without this fix, the following warning is triggered:
=============================
WARNING: suspicious RCU usage
6.14.0-rc3 #55 Not tainted
-----------------------------
drivers/iommu/intel/dmar.c:2046 RCU-list traversed in non-reader section!!
other info that might help us debug this:
rcu_scheduler_active = 1, debug_locks = 1
2 locks held by cpuhp/1/23:
#0: ffffffff84a67c50 (cpu_hotplug_lock){++++}-{0:0}, at: cpuhp_thread_fun+0x87/0x2c0
#1: ffffffff84a6a380 (cpuhp_state-up){+.+.}-{0:0}, at: cpuhp_thread_fun+0x87/0x2c0
stack backtrace:
CPU: 1 UID: 0 PID: 23 Comm: cpuhp/1 Not tainted 6.14.0-rc3 #55
Call Trace:
<TASK>
dump_stack_lvl+0xb7/0xd0
lockdep_rcu_suspicious+0x159/0x1f0
? __pfx_enable_drhd_fault_handling+0x10/0x10
enable_drhd_fault_handling+0x151/0x180
cpuhp_invoke_callback+0x1df/0x990
cpuhp_thread_fun+0x1ea/0x2c0
smpboot_thread_fn+0x1f5/0x2e0
? __pfx_smpboot_thread_fn+0x10/0x10
kthread+0x12a/0x2d0
? __pfx_kthread+0x10/0x10
ret_from_fork+0x4a/0x60
? __pfx_kthread+0x10/0x10
ret_from_fork_asm+0x1a/0x30
</TASK>
Holding the lock in enable_drhd_fault_handling() triggers a lockdep splat
about a possible deadlock between dmar_global_lock and cpu_hotplug_lock.
This is avoided by not holding dmar_global_lock when calling
iommu_device_register(), which initiates the device probe process.
Fixes: d74169ceb0d2 ("iommu/vt-d: Allocate DMAR fault interrupts locally")
Reported-and-tested-by: Ido Schimmel <idosch@nvidia.com>
Closes: https://lore.kernel.org/linux-iommu/Zx9OwdLIc_VoQ0-a@shredder.mtl.com/
Tested-by: Breno Leitao <leitao@debian.org>
Cc: stable@vger.kernel.org
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20250218022422.2315082-1-baolu.lu@linux.intel.com
Tested-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
| -rw-r--r-- | drivers/iommu/intel/dmar.c | 1 | ||||
| -rw-r--r-- | drivers/iommu/intel/iommu.c | 7 |
2 files changed, 8 insertions, 0 deletions
diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c index 9f424acf474e..e540092d664d 100644 --- a/drivers/iommu/intel/dmar.c +++ b/drivers/iommu/intel/dmar.c @@ -2043,6 +2043,7 @@ int enable_drhd_fault_handling(unsigned int cpu) /* * Enable fault control interrupt. */ + guard(rwsem_read)(&dmar_global_lock); for_each_iommu(iommu, drhd) { u32 fault_status; int ret; diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c index 4d8d4593c9c8..bf1f0c814348 100644 --- a/drivers/iommu/intel/iommu.c +++ b/drivers/iommu/intel/iommu.c @@ -3146,7 +3146,14 @@ int __init intel_iommu_init(void) iommu_device_sysfs_add(&iommu->iommu, NULL, intel_iommu_groups, "%s", iommu->name); + /* + * The iommu device probe is protected by the iommu_probe_device_lock. + * Release the dmar_global_lock before entering the device probe path + * to avoid unnecessary lock order splat. + */ + up_read(&dmar_global_lock); iommu_device_register(&iommu->iommu, &intel_iommu_ops, NULL); + down_read(&dmar_global_lock); iommu_pmu_register(iommu); } |