iommu/arm-smmu: add support for DOMAIN_ATTR_NESTING attribute

When domains are set with the DOMAIN_ATTR_NESTING flag, we must ensure
that we allocate them to stage-2 context banks if the hardware permits
it.

This patch adds support for the attribute to the ARM SMMU driver, with
the actual stage being determined depending on the features supported
by the hardware.

Change-Id: I17e027388efbeaae65886160f35a5f8068fd7734
Signed-off-by: Will Deacon <will.deacon@arm.com>
Git-commit: c752ce45b213de8532baaf987ba930638f77c439
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
[mitchelh: resolved conflicts with our existing domain attr
 setter/getter, and locking differences]
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>

1 files changed, 54 insertions, 9 deletions

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 0a8952f77536..ef35f89dafd7 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -482,9 +482,16 @@ struct arm_smmu_cfg {
 #define ARM_SMMU_CB_ASID(cfg)		((cfg)->cbndx + 1)
 #define ARM_SMMU_CB_VMID(cfg)		((cfg)->cbndx + 2)
 
+enum arm_smmu_domain_stage {
+	ARM_SMMU_DOMAIN_S1 = 0,
+	ARM_SMMU_DOMAIN_S2,
+	ARM_SMMU_DOMAIN_NESTED,
+};
+
 struct arm_smmu_domain {
 	struct arm_smmu_device		*smmu;
 	struct arm_smmu_cfg		cfg;
+	enum arm_smmu_domain_stage	stage;
 	struct mutex			lock;
 	u32				attributes;
 };
@@ -1187,19 +1194,46 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
 	if (smmu_domain->smmu)
 		goto out;
 
-	if (smmu->features & ARM_SMMU_FEAT_TRANS_NESTED) {
+	/*
+	 * Mapping the requested stage onto what we support is surprisingly
+	 * complicated, mainly because the spec allows S1+S2 SMMUs without
+	 * support for nested translation. That means we end up with the
+	 * following table:
+	 *
+	 * Requested        Supported        Actual
+	 *     S1               N              S1
+	 *     S1             S1+S2            S1
+	 *     S1               S2             S2
+	 *     S1               S1             S1
+	 *     N                N              N
+	 *     N              S1+S2            S2
+	 *     N                S2             S2
+	 *     N                S1             S1
+	 *
+	 * Note that you can't actually request stage-2 mappings.
+	 */
+	if (!(smmu->features & ARM_SMMU_FEAT_TRANS_S1))
+		smmu_domain->stage = ARM_SMMU_DOMAIN_S2;
+	if (!(smmu->features & ARM_SMMU_FEAT_TRANS_S2))
+		smmu_domain->stage = ARM_SMMU_DOMAIN_S1;
+
+	switch (smmu_domain->stage) {
+	case ARM_SMMU_DOMAIN_S1:
+		cfg->cbar = CBAR_TYPE_S1_TRANS_S2_BYPASS;
+		start = smmu->num_s2_context_banks;
+		break;
+	case ARM_SMMU_DOMAIN_NESTED:
 		/*
 		 * We will likely want to change this if/when KVM gets
 		 * involved.
 		 */
-		cfg->cbar = CBAR_TYPE_S1_TRANS_S2_BYPASS;
-		start = smmu->num_s2_context_banks;
-	} else if (smmu->features & ARM_SMMU_FEAT_TRANS_S1) {
-		cfg->cbar = CBAR_TYPE_S1_TRANS_S2_BYPASS;
-		start = smmu->num_s2_context_banks;
-	} else {
+	case ARM_SMMU_DOMAIN_S2:
 		cfg->cbar = CBAR_TYPE_S2_TRANS;
 		start = 0;
+		break;
+	default:
+		ret = -EINVAL;
+		goto out;
 	}
 
 	ret = __arm_smmu_alloc_bitmap(smmu->context_map, start,
@@ -2175,6 +2209,9 @@ static int arm_smmu_domain_get_attr(struct iommu_domain *domain,
 	struct arm_smmu_domain *smmu_domain = domain->priv;
 
 	switch (attr) {
+	case DOMAIN_ATTR_NESTING:
+		*(int *)data = (smmu_domain->stage == ARM_SMMU_DOMAIN_NESTED);
+		return 0;
 	case DOMAIN_ATTR_COHERENT_HTW_DISABLE:
 		*((int *)data) = !!(smmu_domain->attributes &
 				(1 << DOMAIN_ATTR_COHERENT_HTW_DISABLE));
@@ -2193,6 +2230,14 @@ static int arm_smmu_domain_set_attr(struct iommu_domain *domain,
 	struct arm_smmu_domain *smmu_domain = domain->priv;
 
 	switch (attr) {
+	case DOMAIN_ATTR_NESTING:
+		if (smmu_domain->smmu)
+			return -EPERM;
+		if (*(int *)data)
+			smmu_domain->stage = ARM_SMMU_DOMAIN_NESTED;
+		else
+			smmu_domain->stage = ARM_SMMU_DOMAIN_S1;
+		return 0;
 	case DOMAIN_ATTR_COHERENT_HTW_DISABLE:
 	{
 		struct arm_smmu_device *smmu;
@@ -2238,8 +2283,8 @@ static struct iommu_ops arm_smmu_ops = {
 	.domain_get_attr	= arm_smmu_domain_get_attr,
 	.domain_set_attr	= arm_smmu_domain_set_attr,
 	.pgsize_bitmap		= (SECTION_SIZE |
-			   ARM_SMMU_PTE_CONT_SIZE |
-			   PAGE_SIZE),
+				   ARM_SMMU_PTE_CONT_SIZE |
+				   PAGE_SIZE),
 };
 
 static void arm_smmu_device_reset(struct arm_smmu_device *smmu)