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powerpc/iommu: Annotate nested lock for lockdep
[ Upstream commit cc7130bf11
]
The IOMMU table is divided into pools for concurrent mappings and each
pool has a separate spinlock. When taking the ownership of an IOMMU group
to pass through a device to a VM, we lock these spinlocks which triggers
a false negative warning in lockdep (below).
This fixes it by annotating the large pool's spinlock as a nest lock
which makes lockdep not complaining when locking nested locks if
the nest lock is locked already.
===
WARNING: possible recursive locking detected
5.11.0-le_syzkaller_a+fstn1 #100 Not tainted
--------------------------------------------
qemu-system-ppc/4129 is trying to acquire lock:
c0000000119bddb0 (&(p->lock)/1){....}-{2:2}, at: iommu_take_ownership+0xac/0x1e0
but task is already holding lock:
c0000000119bdd30 (&(p->lock)/1){....}-{2:2}, at: iommu_take_ownership+0xac/0x1e0
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&(p->lock)/1);
lock(&(p->lock)/1);
===
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210301063653.51003-1-aik@ozlabs.ru
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
parent
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1 changed files with 2 additions and 2 deletions
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@ -1055,7 +1055,7 @@ int iommu_take_ownership(struct iommu_table *tbl)
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spin_lock_irqsave(&tbl->large_pool.lock, flags);
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for (i = 0; i < tbl->nr_pools; i++)
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spin_lock(&tbl->pools[i].lock);
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spin_lock_nest_lock(&tbl->pools[i].lock, &tbl->large_pool.lock);
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if (tbl->it_offset == 0)
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clear_bit(0, tbl->it_map);
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@ -1084,7 +1084,7 @@ void iommu_release_ownership(struct iommu_table *tbl)
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spin_lock_irqsave(&tbl->large_pool.lock, flags);
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for (i = 0; i < tbl->nr_pools; i++)
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spin_lock(&tbl->pools[i].lock);
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spin_lock_nest_lock(&tbl->pools[i].lock, &tbl->large_pool.lock);
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memset(tbl->it_map, 0, sz);
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