On 2022-04-17 10:04, Ashish Mhetre wrote:
Tegra194 and Tegra234 SoCs have the erratum that causes walk cache
entries to not be invalidated correctly. The problem is that the walk
cache index generated for IOVA is not same across translation and
invalidation requests. This is leading to page faults when PMD entry is
released during unmap and populated with new PTE table during subsequent
map request. Disabling large page mappings avoids the release of PMD
entry and avoid translations seeing stale PMD entry in walk cache.
Fix this by limiting the page mappings to PAGE_SIZE for Tegra194 and
Tegra234 devices. This is recommended fix from Tegra hardware design
team.
Is this related to any of the several known MMU-500 invalidation errata,
or is it definitely specific to something NVIDIA have done with their
integration?
Co-developed-by: Pritesh Raithatha <praithatha@xxxxxxxxxx>
Signed-off-by: Pritesh Raithatha <praithatha@xxxxxxxxxx>
Signed-off-by: Ashish Mhetre <amhetre@xxxxxxxxxx>
---
drivers/iommu/arm/arm-smmu/arm-smmu-nvidia.c | 23 ++++++++++++++++++++
drivers/iommu/arm/arm-smmu/arm-smmu.c | 3 +++
drivers/iommu/arm/arm-smmu/arm-smmu.h | 1 +
3 files changed, 27 insertions(+)
diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-nvidia.c b/drivers/iommu/arm/arm-smmu/arm-smmu-nvidia.c
index 01e9b50b10a1..b7a3d06da2f4 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu-nvidia.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu-nvidia.c
@@ -258,6 +258,27 @@ static void nvidia_smmu_probe_finalize(struct arm_smmu_device *smmu, struct devi
dev_name(dev), err);
}
+static void nvidia_smmu_cfg_pgsize_bitmap(struct arm_smmu_device *smmu)
+{
+ const struct device_node *np = smmu->dev->of_node;
+
+ /*
+ * Tegra194 and Tegra234 SoCs have the erratum that causes walk cache
+ * entries to not be invalidated correctly. The problem is that the walk
+ * cache index generated for IOVA is not same across translation and
+ * invalidation requests. This is leading to page faults when PMD entry
+ * is released during unmap and populated with new PTE table during
+ * subsequent map request. Disabling large page mappings avoids the
+ * release of PMD entry and avoid translations seeing stale PMD entry in
+ * walk cache.
+ * Fix this by limiting the page mappings to PAGE_SIZE on Tegra194 and
+ * Tegra234.
+ */
+ if (of_device_is_compatible(np, "nvidia,tegra234-smmu") ||
+ of_device_is_compatible(np, "nvidia,tegra194-smmu"))
+ smmu->pgsize_bitmap = PAGE_SIZE;
+}
+
static const struct arm_smmu_impl nvidia_smmu_impl = {
.read_reg = nvidia_smmu_read_reg,
.write_reg = nvidia_smmu_write_reg,
@@ -268,10 +289,12 @@ static const struct arm_smmu_impl nvidia_smmu_impl = {
.global_fault = nvidia_smmu_global_fault,
.context_fault = nvidia_smmu_context_fault,
.probe_finalize = nvidia_smmu_probe_finalize,
+ .cfg_pgsize_bitmap = nvidia_smmu_cfg_pgsize_bitmap,
};
static const struct arm_smmu_impl nvidia_smmu_single_impl = {
.probe_finalize = nvidia_smmu_probe_finalize,
+ .cfg_pgsize_bitmap = nvidia_smmu_cfg_pgsize_bitmap,
};
struct arm_smmu_device *nvidia_smmu_impl_init(struct arm_smmu_device *smmu)
diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
index 568cce590ccc..3692a19a588a 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
@@ -1872,6 +1872,9 @@ static int arm_smmu_device_cfg_probe(struct arm_smmu_device *smmu)
if (smmu->features & ARM_SMMU_FEAT_FMT_AARCH64_64K)
smmu->pgsize_bitmap |= SZ_64K | SZ_512M;
+ if (smmu->impl && smmu->impl->cfg_pgsize_bitmap)
+ smmu->impl->cfg_pgsize_bitmap(smmu);
I'm not the biggest fan of adding a super-specific hook for this, when
it seems like it could just as easily be handled in the init_context
hook, which is where it is precisely for the purpose of mangling the
pgtable_cfg to influence io-pgtable's behaviour.
Thanks,
Robin.
+
if (arm_smmu_ops.pgsize_bitmap == -1UL)
arm_smmu_ops.pgsize_bitmap = smmu->pgsize_bitmap;
else
diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.h b/drivers/iommu/arm/arm-smmu/arm-smmu.h
index 2b9b42fb6f30..5d9b03024969 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.h
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.h
@@ -442,6 +442,7 @@ struct arm_smmu_impl {
void (*write_s2cr)(struct arm_smmu_device *smmu, int idx);
void (*write_sctlr)(struct arm_smmu_device *smmu, int idx, u32 reg);
void (*probe_finalize)(struct arm_smmu_device *smmu, struct device *dev);
+ void (*cfg_pgsize_bitmap)(struct arm_smmu_device *smmu);
};
#define INVALID_SMENDX -1
