[PATCH AUTOSEL 5.6 115/129] iommu/vt-d: Silence RCU-list debugging warning in dmar_find_atsr()

Sasha Levin
2020-04-15T12:43:48Z

From: Qian Cai <cai@lca.pw>

[ Upstream commit c6f4ebdeba4cff590594df931ff1ee610c426431 ]

dmar_find_atsr() calls list_for_each_entry_rcu() outside of an RCU read
side critical section but with dmar_global_lock held. Silence this
false positive.

drivers/iommu/intel-iommu.c:4504 RCU-list traversed in non-reader section!!
1 lock held by swapper/0/1:
#0: ffffffff9755bee8 (dmar_global_lock){+.+.}, at: intel_iommu_init+0x1a6/0xe19

Call Trace:
dump_stack+0xa4/0xfe
lockdep_rcu_suspicious+0xeb/0xf5
dmar_find_atsr+0x1ab/0x1c0
dmar_parse_one_atsr+0x64/0x220
dmar_walk_remapping_entries+0x130/0x380
dmar_table_init+0x166/0x243
intel_iommu_init+0x1ab/0xe19
pci_iommu_init+0x1a/0x44
do_one_initcall+0xae/0x4d0
kernel_init_freeable+0x412/0x4c5
kernel_init+0x19/0x193

Signed-off-by: Qian Cai <cai@lca.pw>
Acked-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/iommu/intel-iommu.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 4be5494786918..ef0a5246700e5 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4501,7 +4501,8 @@ static struct dmar_atsr_unit *dmar_find_atsr(struct acpi_dmar_atsr *atsr)
struct dmar_atsr_unit *atsru;
struct acpi_dmar_atsr *tmp;

- list_for_each_entry_rcu(atsru, &dmar_atsr_units, list) {
+ list_for_each_entry_rcu(atsru, &dmar_atsr_units, list,
+ dmar_rcu_check()) {
tmp = (struct acpi_dmar_atsr *)atsru->hdr;
if (atsr->segment != tmp->segment)
continue;
--
2.20.1