[PATCH v4 3/3] iommu/arm-smmu-v3: Issue CFGI/TLBI twice on Tegra264

[Ashish Mhetre <amhetre@nvidia.com>]

Apply the workaround for Tegra264 erratum ARM_SMMU_OPT_REPEAT_TLBI_CFGI
by issuing every CFGI/TLBI cmdlist twice on affected SMMU instances,
with CMD_SYNC after each. The erratum requires this exact sequencing:

    TLBI/CFGI ... CMD_SYNC TLBI/CFGI ... CMD_SYNC

Rename the existing arm_smmu_cmdq_issue_cmdlist() to
__arm_smmu_cmdq_issue_cmdlist() and add a thin wrapper that, on
affected SMMUs and when @sync is true with @n > 0, re-issues the
same cmdlist a second time when arm_smmu_erratum_cmd_needs_repeating()
is true. The @n > 0 gate is needed because arm_smmu_cmdq_batch_add_cmd_p()
can call arm_smmu_cmdq_issue_cmdlist() with @n == 0 and @sync == true
to flush a bare CMD_SYNC when the next command is not supported by
the batch's pre-selected cmdq; the repeat path must not inspect
cmds[0] in that case. The static-key gate inside the predicate means
the wrapper compiles to a single tested branch on unaffected kernels.

For the in-tree batching path, register the new condition with
arm_smmu_cmdq_batch_force_sync() so that a full batch carrying
CFGI/TLBI commands flushes with sync=true.

For the iommufd VSMMU path add an arm_vsmmu_can_batch_cmd() predicate
that splits the iommufd batch at every "needs repeating" transition,
so the wrapper's per-batch decision based on the first command stays
correct even when userspace mixes opcode classes.

Also document the erratum in Documentation/arch/arm64/silicon-errata.rst.

Suggested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Ashish Mhetre <amhetre@nvidia.com>
---
 Documentation/arch/arm64/silicon-errata.rst   |  2 ++
 .../arm/arm-smmu-v3/arm-smmu-v3-iommufd.c     | 15 +++++++-
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c   | 35 ++++++++++++++++---
 3 files changed, 47 insertions(+), 5 deletions(-)

diff --git a/Documentation/arch/arm64/silicon-errata.rst b/Documentation/arch/arm64/silicon-errata.rst
index 046a7fa47063..96050886a7d6 100644
--- a/Documentation/arch/arm64/silicon-errata.rst
+++ b/Documentation/arch/arm64/silicon-errata.rst
@@ -268,6 +268,8 @@ stable kernels.
 |                |                 | T241-MPAM-4,    |                             |
 |                |                 | T241-MPAM-6     |                             |
 +----------------+-----------------+-----------------+-----------------------------+
+| NVIDIA         | T264 SMMU       | T264-SMMU-3     | N/A                         |
++----------------+-----------------+-----------------+-----------------------------+
 +----------------+-----------------+-----------------+-----------------------------+
 | Freescale/NXP  | LS2080A/LS1043A | A-008585        | FSL_ERRATUM_A008585         |
 +----------------+-----------------+-----------------+-----------------------------+
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
index 1e9f7d2de344..11d22acae613 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
@@ -350,6 +350,18 @@ static int arm_vsmmu_convert_user_cmd(struct arm_vsmmu *vsmmu,
 	return 0;
 }
 
+static bool arm_vsmmu_can_batch_cmd(struct arm_smmu_device *smmu,
+				    struct arm_vsmmu_invalidation_cmd *last,
+				    struct arm_vsmmu_invalidation_cmd *next)
+{
+	struct arm_smmu_cmd next_cmd = {
+		.data[0] = le64_to_cpu(next->ucmd.cmd[0]),
+	};
+
+	return arm_smmu_erratum_cmd_needs_repeating(smmu, &last->cmd) ==
+	       arm_smmu_erratum_cmd_needs_repeating(smmu, &next_cmd);
+}
+
 int arm_vsmmu_cache_invalidate(struct iommufd_viommu *viommu,
 			       struct iommu_user_data_array *array)
 {
@@ -382,7 +394,8 @@ int arm_vsmmu_cache_invalidate(struct iommufd_viommu *viommu,
 
 		/* FIXME work in blocks of CMDQ_BATCH_ENTRIES and copy each block? */
 		cur++;
-		if (cur != end && (cur - last) != CMDQ_BATCH_ENTRIES - 1)
+		if (cur != end && (cur - last) != CMDQ_BATCH_ENTRIES - 1 &&
+		    arm_vsmmu_can_batch_cmd(smmu, last, cur))
 			continue;
 
 		/* FIXME always uses the main cmdq rather than trying to group by type */
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 599c835c50d8..041e188b3b30 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -700,10 +700,10 @@ static void arm_smmu_cmdq_write_entries(struct arm_smmu_cmdq *cmdq,
  *   insert their own list of commands then all of the commands from one
  *   CPU will appear before any of the commands from the other CPU.
  */
-int arm_smmu_cmdq_issue_cmdlist(struct arm_smmu_device *smmu,
-				struct arm_smmu_cmdq *cmdq,
-				struct arm_smmu_cmd *cmds, int n,
-				bool sync)
+static int __arm_smmu_cmdq_issue_cmdlist(struct arm_smmu_device *smmu,
+					 struct arm_smmu_cmdq *cmdq,
+					 struct arm_smmu_cmd *cmds, int n,
+					 bool sync)
 {
 	struct arm_smmu_cmd cmd_sync;
 	u32 prod;
@@ -822,6 +822,28 @@ int arm_smmu_cmdq_issue_cmdlist(struct arm_smmu_device *smmu,
 	return ret;
 }
 
+int arm_smmu_cmdq_issue_cmdlist(struct arm_smmu_device *smmu,
+				struct arm_smmu_cmdq *cmdq,
+				struct arm_smmu_cmd *cmds, int n,
+				bool sync)
+{
+	int ret = __arm_smmu_cmdq_issue_cmdlist(smmu, cmdq, cmds, n, sync);
+
+	/*
+	 * arm_smmu_cmdq_batch_add_cmd_p() can flush its current batch with
+	 * sync=true and n=0 (bare SYNC) when the next command is not
+	 * supported by the batch's pre-selected cmdq, so the repeat path
+	 * must not inspect cmds[0].
+	 */
+	if (!n || ret || !sync)
+		return ret;
+
+	if (arm_smmu_erratum_cmd_needs_repeating(smmu, &cmds[0]))
+		ret = __arm_smmu_cmdq_issue_cmdlist(smmu, cmdq, cmds, n, sync);
+
+	return ret;
+}
+
 static int arm_smmu_cmdq_issue_cmd_p(struct arm_smmu_device *smmu,
 				     struct arm_smmu_cmd *cmd, bool sync)
 {
@@ -862,6 +884,11 @@ static bool arm_smmu_cmdq_batch_force_sync(struct arm_smmu_device *smmu,
 	    (smmu->options & ARM_SMMU_OPT_CMDQ_FORCE_SYNC))
 		return true;
 
+	/* See ARM_SMMU_OPT_REPEAT_TLBI_CFGI */
+	if (cmds->num == CMDQ_BATCH_ENTRIES &&
+	    arm_smmu_erratum_cmd_needs_repeating(smmu, &cmds->cmds[0]))
+		return true;
+
 	return false;
 }
 
-- 
2.50.1