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@vger.kernel.org Fixes: 9ce27afc0830 ("iommu/arm-smmu-v3: Add support for PCI ATS") Signed-off-by: Will Deacon will@kernel.org --- 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;