linux-kernel - [PATCH v1] iommu/arm-smmu-v3: Allow default substream bypass with a pasid support

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Message-ID: <20230627033326.5236-1-nicolinc@nvidia.com>
Date:   Mon, 26 Jun 2023 20:33:26 -0700
From:   Nicolin Chen <nicolinc@...dia.com>
To:     <robin.murphy@....com>, <will@...nel.org>
CC:     <jgg@...dia.com>, <joro@...tes.org>,
        <shameerali.kolothum.thodi@...wei.com>, <yangyicong@...ilicon.com>,
        <jean-philippe@...aro.org>, <linux-arm-kernel@...ts.infradead.org>,
        <iommu@...ts.linux.dev>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v1] iommu/arm-smmu-v3: Allow default substream bypass with a pasid support

When an iommu_domain is set to IOMMU_DOMAIN_IDENTITY, the driver would
skip the allocation of a CD table and set the CONFIG field of the STE
to STRTAB_STE_0_CFG_BYPASS. This works well for devices that only have
one substream, i.e. PASID disabled.

However, there could be a use case, for a pasid capable device, that
allows bypassing the translation at the default substream while still
enabling the pasid feature, which means the driver should not skip the
allocation of a CD table nor simply bypass the CONFIG field. Instead,
the S1DSS field should be set to STRTAB_STE_1_S1DSS_BYPASS and the
SHCFG field should be set to STRTAB_STE_1_SHCFG_INCOMING.

Add s1dss and shcfg in struct arm_smmu_s1_cfg, to allow configurations
in the finalise() to support that use case. Then, set them accordingly
depending on the iommu_domain->type and the master->ssid_bits.

Also, add STRTAB_STE_1_SHCFG_NONSHAREABLE of the default configuration
to distinguish from STRTAB_STE_1_SHCFG_INCOMING of the bypass one.

Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 18 +++++++++++++++---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h |  3 +++
 2 files changed, 18 insertions(+), 3 deletions(-)

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 9b0dc3505601..8dc7934a0175 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -1350,11 +1350,12 @@ static void arm_smmu_write_strtab_ent(struct arm_smmu_master *master, u32 sid,
 
 		BUG_ON(ste_live);
 		dst[1] = cpu_to_le64(
-			 FIELD_PREP(STRTAB_STE_1_S1DSS, STRTAB_STE_1_S1DSS_SSID0) |
+			 FIELD_PREP(STRTAB_STE_1_S1DSS, s1_cfg->s1dss) |
 			 FIELD_PREP(STRTAB_STE_1_S1CIR, STRTAB_STE_1_S1C_CACHE_WBRA) |
 			 FIELD_PREP(STRTAB_STE_1_S1COR, STRTAB_STE_1_S1C_CACHE_WBRA) |
 			 FIELD_PREP(STRTAB_STE_1_S1CSH, ARM_SMMU_SH_ISH) |
-			 FIELD_PREP(STRTAB_STE_1_STRW, strw));
+			 FIELD_PREP(STRTAB_STE_1_STRW, strw) |
+			 FIELD_PREP(STRTAB_STE_1_SHCFG, s1_cfg->shcfg));
 
 		if (smmu->features & ARM_SMMU_FEAT_STALLS &&
 		    !master->stall_enabled)
@@ -2119,6 +2120,13 @@ static int arm_smmu_domain_finalise_s1(struct arm_smmu_domain *smmu_domain,
 		goto out_unlock;
 
 	cfg->s1cdmax = master->ssid_bits;
+	if (smmu_domain->domain.type == IOMMU_DOMAIN_IDENTITY) {
+		cfg->s1dss = STRTAB_STE_1_S1DSS_BYPASS;
+		cfg->shcfg = STRTAB_STE_1_SHCFG_INCOMING;
+	} else {
+		cfg->s1dss = STRTAB_STE_1_S1DSS_SSID0;
+		cfg->shcfg = STRTAB_STE_1_SHCFG_NONSHAREABLE;
+	}
 
 	smmu_domain->stall_enabled = master->stall_enabled;
 
@@ -2198,7 +2206,11 @@ static int arm_smmu_domain_finalise(struct iommu_domain *domain,
 	struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
 	struct arm_smmu_device *smmu = smmu_domain->smmu;
 
-	if (domain->type == IOMMU_DOMAIN_IDENTITY) {
+	/*
+	 * A master with a pasid capability might need a CD table, so only set
+	 * ARM_SMMU_DOMAIN_BYPASS if IOMMU_DOMAIN_IDENTITY and non-pasid master
+	 */
+	if (domain->type == IOMMU_DOMAIN_IDENTITY && !master->ssid_bits) {
 		smmu_domain->stage = ARM_SMMU_DOMAIN_BYPASS;
 		return 0;
 	}
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
index dcab85698a4e..8052d02770d0 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -244,6 +244,7 @@
 #define STRTAB_STE_1_STRW_EL2		2UL
 
 #define STRTAB_STE_1_SHCFG		GENMASK_ULL(45, 44)
+#define STRTAB_STE_1_SHCFG_NONSHAREABLE	0UL
 #define STRTAB_STE_1_SHCFG_INCOMING	1UL
 
 #define STRTAB_STE_2_S2VMID		GENMASK_ULL(15, 0)
@@ -601,6 +602,8 @@ struct arm_smmu_s1_cfg {
 	struct arm_smmu_ctx_desc_cfg	cdcfg;
 	struct arm_smmu_ctx_desc	cd;
 	u8				s1fmt;
+	u8				s1dss;
+	u8				shcfg;
 	u8				s1cdmax;
 };
 
-- 
2.41.0