Detecting the ATS capability of the SMMU at probe time introduces a
spinlock into the ->unmap() fast path, even when ATS is not actually
in use. Furthermore, the ATC invalidation that exists is broken, as it
occurs before invalidation of the main SMMU TLB which leaves a window
where the ATC can be repopulated with stale entries.
Given that ATS is both a new feature and a specialist sport, disable it
for now whilst we fix it properly in subsequent patches. Since PRI
requires ATS, disable that too.
Cc: <stable@xxxxxxxxxxxxxxx>
Fixes: 9ce27afc0830 ("iommu/arm-smmu-v3: Add support for PCI ATS")
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
---
drivers/iommu/arm-smmu-v3.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 3402b1bc8e94..7a368059cd7d 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -3295,11 +3295,13 @@ static int arm_smmu_device_hw_probe(struct arm_smmu_device *smmu)
}
/* Boolean feature flags */
+#if 0 /* ATS invalidation is slow and broken */
if (IS_ENABLED(CONFIG_PCI_PRI) && reg & IDR0_PRI)
smmu->features |= ARM_SMMU_FEAT_PRI;
if (IS_ENABLED(CONFIG_PCI_ATS) && reg & IDR0_ATS)
smmu->features |= ARM_SMMU_FEAT_ATS;
+#endif
if (reg & IDR0_SEV)
smmu->features |= ARM_SMMU_FEAT_SEV;
--
2.11.0
