6.12-stable review patch. If anyone has any objections, please let me know.
------------------
From: Luis Claudio R. Goncalves <lgoncalv@xxxxxxxxxx>
commit 1f806218164d1bb93f3db21eaf61254b08acdf03 upstream.
During boot some of the calls to tegra241_cmdqv_get_cmdq() will happen
in preemptible context. As this function calls smp_processor_id(), if
CONFIG_DEBUG_PREEMPT is enabled, these calls will trigger a series of
"BUG: using smp_processor_id() in preemptible" backtraces.
As tegra241_cmdqv_get_cmdq() only calls smp_processor_id() to use the
CPU number as a factor to balance out traffic on cmdq usage, it is safe
to use raw_smp_processor_id() here.
Cc: <stable@xxxxxxxxxxxxxxx>
Fixes: 918eb5c856f6 ("iommu/arm-smmu-v3: Add in-kernel support for NVIDIA Tegra241 (Grace) CMDQV")
Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@xxxxxxxxxx>
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Reviewed-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
Tested-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
Link: https://lore.kernel.org/r/Z1L1mja3nXzsJ0Pk@xxxxxxxx
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c b/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
index c8ec74f089f3..6e41ddaa24d6 100644
--- a/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
+++ b/drivers/iommu/arm/arm-smmu-v3/tegra241-cmdqv.c
@@ -339,7 +339,7 @@ tegra241_cmdqv_get_cmdq(struct arm_smmu_device *smmu,
* one CPU at a time can enter the process, while the others
* will be spinning at the same lock.
*/
- lidx = smp_processor_id() % cmdqv->num_lvcmdqs_per_vintf;
+ lidx = raw_smp_processor_id() % cmdqv->num_lvcmdqs_per_vintf;
vcmdq = vintf->lvcmdqs[lidx];
if (!vcmdq || !READ_ONCE(vcmdq->enabled))
return NULL;
--
2.47.1
