From: Alexey Kardashevskiy Date: Mon, 1 Mar 2021 06:36:53 +0000 (+1100) Subject: powerpc/iommu: Annotate nested lock for lockdep X-Git-Tag: v5.11.22~230 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8089cb59dde9515df2877a5cf99e6e366dd09f00;p=thirdparty%2Fkernel%2Fstable.git powerpc/iommu: Annotate nested lock for lockdep [ Upstream commit cc7130bf119add37f36238343a593b71ef6ecc1e ] 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 Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210301063653.51003-1-aik@ozlabs.ru Signed-off-by: Sasha Levin --- diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c index 5b69a6a72a0e2..6806eefa52ceb 100644 --- a/arch/powerpc/kernel/iommu.c +++ b/arch/powerpc/kernel/iommu.c @@ -1050,7 +1050,7 @@ int iommu_take_ownership(struct iommu_table *tbl) spin_lock_irqsave(&tbl->large_pool.lock, flags); for (i = 0; i < tbl->nr_pools; i++) - spin_lock(&tbl->pools[i].lock); + spin_lock_nest_lock(&tbl->pools[i].lock, &tbl->large_pool.lock); iommu_table_release_pages(tbl); @@ -1078,7 +1078,7 @@ void iommu_release_ownership(struct iommu_table *tbl) spin_lock_irqsave(&tbl->large_pool.lock, flags); for (i = 0; i < tbl->nr_pools; i++) - spin_lock(&tbl->pools[i].lock); + spin_lock_nest_lock(&tbl->pools[i].lock, &tbl->large_pool.lock); memset(tbl->it_map, 0, sz);