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charset="utf-8" From: Nicolin Chen arm_smmu_cmdq_batch_add_cmd_p() carries two distinct reasons for flushing the current batch with a CMD_SYNC before appending the new command: - The batch's pre-assigned cmdq does not support the new command. - The Arm erratum 2812531 workaround (ARM_SMMU_OPT_CMDQ_FORCE_SYNC) forces a SYNC at one entry before the batch is full. Lift those checks into a new arm_smmu_cmdq_batch_force_sync() helper so that adding another force-sync condition becomes a one-line addition. No functional change. Signed-off-by: Nicolin Chen Signed-off-by: Ashish Mhetre Reviewed-by: Jason Gunthorpe --- drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 23 +++++++++++++++------ 1 file changed, 17 insertions(+), 6 deletions(-) diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/ar= m/arm-smmu-v3/arm-smmu-v3.c index 57b750ebcd3d..dd7475c50afc 100644 --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c @@ -847,16 +847,27 @@ static void arm_smmu_cmdq_batch_init_cmd(struct arm_s= mmu_device *smmu, cmds->cmdq =3D arm_smmu_get_cmdq(smmu, cmd); } =20 +static bool arm_smmu_cmdq_batch_force_sync(struct arm_smmu_device *smmu, + struct arm_smmu_cmdq_batch *cmds, + struct arm_smmu_cmd *cmd) +{ + /* The batch's pre-assigned cmdq doesn't support the new command */ + if (!arm_smmu_cmdq_supports_cmd(cmds->cmdq, cmd)) + return true; + + /* Arm erratum 2812531 */ + if (cmds->num =3D=3D CMDQ_BATCH_ENTRIES - 1 && + (smmu->options & ARM_SMMU_OPT_CMDQ_FORCE_SYNC)) + return true; + + return false; +} + static void arm_smmu_cmdq_batch_add_cmd_p(struct arm_smmu_device *smmu, struct arm_smmu_cmdq_batch *cmds, struct arm_smmu_cmd *cmd) { - bool force_sync =3D (cmds->num =3D=3D CMDQ_BATCH_ENTRIES - 1) && - (smmu->options & ARM_SMMU_OPT_CMDQ_FORCE_SYNC); - bool unsupported_cmd; - - unsupported_cmd =3D !arm_smmu_cmdq_supports_cmd(cmds->cmdq, cmd); - if (force_sync || unsupported_cmd) { + if (arm_smmu_cmdq_batch_force_sync(smmu, cmds, cmd)) { arm_smmu_cmdq_issue_cmdlist(smmu, cmds->cmdq, cmds->cmds, cmds->num, true); arm_smmu_cmdq_batch_init_cmd(smmu, cmds, cmd); --=20 2.50.1 From nobody Sat Jul 25 19:27:03 2026 Received: from MW6PR02CU001.outbound.protection.outlook.com (mail-westus2azon11012063.outbound.protection.outlook.com [52.101.48.63]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 71E36378814; Tue, 14 Jul 2026 10:42:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; 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charset="utf-8" Tegra264 SMMU instances need every CFGI/TLBI command sequence issued twice, with the second issue executing only after the first issue's CMD_SYNC has completed: TLBI/CFGI ... CMD_SYNC TLBI/CFGI ... CMD_SYNC ATC_INV is not affected and must never be doubled. Add arm_smmu_erratum_repeat_tlbi_cfgi_key and an arm_smmu_erratum_cmd_needs_repeating() helper that gates on the static key first and then range-checks the opcode (CFGI_STE .. ATC_INV), so subsequent changes wiring the workaround into the CMDQ submission and iommufd batching paths can share a single predicate. Rename the existing arm_smmu_cmdq_issue_cmdlist() to __arm_smmu_cmdq_issue_cmdlist() and add a thin wrapper that re-issues the same cmdlist a second time when the predicate fires. Register the new condition with arm_smmu_cmdq_batch_force_sync() and add arm_vsmmu_can_batch_cmd() so iommufd batches split at every "needs repeating" transition. No callers enable the static key yet, so there is no functional change. A subsequent change will enable the key on affected instances. Suggested-by: Nicolin Chen Reviewed-by: Nicolin Chen Signed-off-by: Ashish Mhetre Reviewed-by: Jason Gunthorpe --- .../arm/arm-smmu-v3/arm-smmu-v3-iommufd.c | 14 ++++- drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 57 +++++++++++++++++-- drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 1 + 3 files changed, 67 insertions(+), 5 deletions(-) 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..143f0d015aeb 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 +350,17 @@ static int arm_vsmmu_convert_user_cmd(struct arm_vsmmu= *vsmmu, return 0; } =20 +static bool arm_vsmmu_can_batch_cmd(struct arm_vsmmu_invalidation_cmd *las= t, + struct arm_vsmmu_invalidation_cmd *next) +{ + struct arm_smmu_cmd next_cmd =3D { + .data[0] =3D le64_to_cpu(next->ucmd.cmd[0]), + }; + + return arm_smmu_erratum_cmd_needs_repeating(&last->cmd) =3D=3D + arm_smmu_erratum_cmd_needs_repeating(&next_cmd); +} + int arm_vsmmu_cache_invalidate(struct iommufd_viommu *viommu, struct iommu_user_data_array *array) { @@ -382,7 +393,8 @@ int arm_vsmmu_cache_invalidate(struct iommufd_viommu *v= iommu, =20 /* FIXME work in blocks of CMDQ_BATCH_ENTRIES and copy each block? */ cur++; - if (cur !=3D end && (cur - last) !=3D CMDQ_BATCH_ENTRIES - 1) + if (cur !=3D end && (cur - last) !=3D CMDQ_BATCH_ENTRIES - 1 && + arm_vsmmu_can_batch_cmd(last, cur)) continue; =20 /* 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/ar= m/arm-smmu-v3/arm-smmu-v3.c index dd7475c50afc..9c49e6412053 100644 --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c @@ -18,6 +18,7 @@ #include #include #include +#include #include #include #include @@ -42,6 +43,14 @@ MODULE_PARM_DESC(disable_msipolling, static const struct iommu_ops arm_smmu_ops; static struct iommu_dirty_ops arm_smmu_dirty_ops; =20 +/* + * Repeat every {CFGI,TLBI};CMD_SYNC command sequence so that the second + * issue executes only after the first issue's CMD_SYNC has completed. + * Does not apply to ATC_INV. The key is global and is enabled from DT + * probe on affected hardware (currently Tegra264 only). + */ +static DEFINE_STATIC_KEY_FALSE(arm_smmu_erratum_repeat_tlbi_cfgi_key); + enum arm_smmu_msi_index { EVTQ_MSI_INDEX, GERROR_MSI_INDEX, @@ -698,10 +707,10 @@ static void arm_smmu_cmdq_write_entries(struct arm_sm= mu_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; @@ -820,6 +829,38 @@ int arm_smmu_cmdq_issue_cmdlist(struct arm_smmu_device= *smmu, return ret; } =20 +bool arm_smmu_erratum_cmd_needs_repeating(struct arm_smmu_cmd *cmd) +{ + u8 opcode; + + if (!static_branch_unlikely(&arm_smmu_erratum_repeat_tlbi_cfgi_key)) + return false; + + opcode =3D FIELD_GET(CMDQ_0_OP, cmd->data[0]); + return opcode >=3D CMDQ_OP_CFGI_STE && opcode < CMDQ_OP_ATC_INV; +} + +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 =3D __arm_smmu_cmdq_issue_cmdlist(smmu, cmdq, cmds, n, sync); + + /* + * A bare CMD_SYNC can be issued with n =3D=3D 0 (e.g. an empty + * batch_submit()), in which case there is no cmds[0] to inspect + * and nothing to repeat. + */ + if (!n || ret || !sync) + return ret; + + if (arm_smmu_erratum_cmd_needs_repeating(&cmds[0])) + ret =3D __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) { @@ -860,6 +901,14 @@ static bool arm_smmu_cmdq_batch_force_sync(struct arm_= smmu_device *smmu, (smmu->options & ARM_SMMU_OPT_CMDQ_FORCE_SYNC)) return true; =20 + /* + * See the description at arm_smmu_erratum_repeat_tlbi_cfgi_key. 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charset="utf-8" Nvidia Tegra264 SMMU is affected by an erratum where a TLB entry can survive an invalidation that races with concurrent traffic targeting the same entry. The hardware-recommended software workaround is to issue every CFGI/TLBI command (each followed by CMD_SYNC) twice, and that infrastructure is already in place behind arm_smmu_erratum_repeat_tlbi_cfgi_key. Neither IDR nor IIDR flags this Tegra264-specific bug, so hardware detection is not possible. Tegra264 is device-tree-only (no ACPI/IORT support) and already has a dedicated "nvidia,tegra264-smmu" compatible, so DT-probe is the only viable detection path. Enable the workaround on instances matching the existing "nvidia,tegra264-smmu" compatible by calling static_branch_enable() on arm_smmu_erratum_repeat_tlbi_cfgi_key. Document the erratum in Documentation/arch/arm64/silicon-errata.rst. Note that since guest-level VCMDQs issue commands directly to the hardware, a guest kernel enabling the CMDQV feature on Tegra264 must apply this workaround as well. Reviewed-by: Nicolin Chen Signed-off-by: Ashish Mhetre Reviewed-by: Jason Gunthorpe --- Documentation/arch/arm64/silicon-errata.rst | 2 ++ drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 4 +++- 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/Documentation/arch/arm64/silicon-errata.rst b/Documentation/ar= ch/arm64/silicon-errata.rst index 014aa1c215a1..076b3947d259 100644 --- a/Documentation/arch/arm64/silicon-errata.rst +++ b/Documentation/arch/arm64/silicon-errata.rst @@ -312,6 +312,8 @@ 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.c b/drivers/iommu/ar= m/arm-smmu-v3/arm-smmu-v3.c index 9c49e6412053..a04dea34479c 100644 --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c @@ -5357,8 +5357,10 @@ static int arm_smmu_device_dt_probe(struct platform_= device *pdev, if (of_dma_is_coherent(dev->of_node)) smmu->features |=3D ARM_SMMU_FEAT_COHERENCY; =20 - if (of_device_is_compatible(dev->of_node, "nvidia,tegra264-smmu")) + if (of_device_is_compatible(dev->of_node, "nvidia,tegra264-smmu")) { tegra_cmdqv_dt_probe(dev->of_node, smmu); + static_branch_enable(&arm_smmu_erratum_repeat_tlbi_cfgi_key); + } =20 return ret; } --=20 2.50.1