6.12-stable review patch. If anyone has any objections, please let me know.
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From: Luis Claudio R. Goncalves lgoncalv@redhat.com
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@vger.kernel.org Fixes: 918eb5c856f6 ("iommu/arm-smmu-v3: Add in-kernel support for NVIDIA Tegra241 (Grace) CMDQV") Signed-off-by: Luis Claudio R. Goncalves lgoncalv@redhat.com Reviewed-by: Jason Gunthorpe jgg@nvidia.com Reviewed-by: Nicolin Chen nicolinc@nvidia.com Tested-by: Nicolin Chen nicolinc@nvidia.com Link: https://lore.kernel.org/r/Z1L1mja3nXzsJ0Pk@uudg.org Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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;