iommu/vt-d: Fix lockdep splat in intel_pasid_get_entry()
The pasid_lock is used to synchronize different threads from modifying a
same pasid directory entry at the same time. It causes below lockdep splat.
[ 83.296538] ========================================================
[ 83.296538] WARNING: possible irq lock inversion dependency detected
[ 83.296539] 5.12.0-rc3+ #25 Tainted: G W
[ 83.296539] --------------------------------------------------------
[ 83.296540] bash/780 just changed the state of lock:
[ 83.296540]
ffffffff82b29c98 (device_domain_lock){..-.}-{2:2}, at:
iommu_flush_dev_iotlb.part.0+0x32/0x110
[ 83.296547] but this lock took another, SOFTIRQ-unsafe lock in the past:
[ 83.296547] (pasid_lock){+.+.}-{2:2}
[ 83.296548]
and interrupts could create inverse lock ordering between them.
[ 83.296549] other info that might help us debug this:
[ 83.296549] Chain exists of:
device_domain_lock --> &iommu->lock --> pasid_lock
[ 83.296551] Possible interrupt unsafe locking scenario:
[ 83.296551] CPU0 CPU1
[ 83.296552] ---- ----
[ 83.296552] lock(pasid_lock);
[ 83.296553] local_irq_disable();
[ 83.296553] lock(device_domain_lock);
[ 83.296554] lock(&iommu->lock);
[ 83.296554] <Interrupt>
[ 83.296554] lock(device_domain_lock);
[ 83.296555]
*** DEADLOCK ***
Fix it by replacing the pasid_lock with an atomic exchange operation.
Reported-and-tested-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20210320020916.640115-1-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>