[PATCH v2 27/40] iommu/arm-smmu-v3: Add SVA feature checking

[Jean-Philippe Brucker <jean-philippe.brucker@arm.com>]

Aggregate all sanity-checks for sharing CPU page tables with the SMMU
under a single ARM_SMMU_FEAT_SVA bit. For PCIe SVA, users also need to
check FEAT_ATS and FEAT_PRI. For platform SVM, they will most likely have
to check FEAT_STALLS.

Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>

---
v1->v2: Add 52-bit PA cap and debug message
---
 drivers/iommu/arm-smmu-v3.c | 72 +++++++++++++++++++++++++++++++++++++
 1 file changed, 72 insertions(+)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 073cba33ae6c..2716e4a4d3f7 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -525,6 +525,7 @@ struct arm_smmu_device {
 #define ARM_SMMU_FEAT_VAX		(1 << 14)
 #define ARM_SMMU_FEAT_E2H		(1 << 15)
 #define ARM_SMMU_FEAT_BTM		(1 << 16)
+#define ARM_SMMU_FEAT_SVA		(1 << 17)
 	u32				features;
 
 #define ARM_SMMU_OPT_SKIP_PREFETCH	(1 << 0)
@@ -2565,6 +2566,74 @@ static int arm_smmu_device_reset(struct arm_smmu_device *smmu, bool bypass)
 	return 0;
 }
 
+static bool arm_smmu_supports_sva(struct arm_smmu_device *smmu)
+{
+	unsigned long reg, fld;
+	unsigned long oas;
+	unsigned long asid_bits;
+
+	u32 feat_mask = ARM_SMMU_FEAT_BTM | ARM_SMMU_FEAT_COHERENCY;
+
+	if ((smmu->features & feat_mask) != feat_mask)
+		return false;
+
+	if (!(smmu->pgsize_bitmap & PAGE_SIZE))
+		return false;
+
+	/*
+	 * Get the smallest PA size of all CPUs (sanitized by cpufeature). We're
+	 * not even pretending to support AArch32 here.
+	 */
+	reg = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1);
+	fld = cpuid_feature_extract_unsigned_field(reg, ID_AA64MMFR0_PARANGE_SHIFT);
+	switch (fld) {
+	case 0x0:
+		oas = 32;
+		break;
+	case 0x1:
+		oas = 36;
+		break;
+	case 0x2:
+		oas = 40;
+		break;
+	case 0x3:
+		oas = 42;
+		break;
+	case 0x4:
+		oas = 44;
+		break;
+	case 0x5:
+		oas = 48;
+		break;
+	case 0x6:
+		oas = 52;
+		break;
+	default:
+		return false;
+	}
+
+	/* abort if MMU outputs addresses greater than what we support. */
+	if (smmu->oas < oas)
+		return false;
+
+	/* We can support bigger ASIDs than the CPU, but not smaller */
+	fld = cpuid_feature_extract_unsigned_field(reg, ID_AA64MMFR0_ASID_SHIFT);
+	asid_bits = fld ? 16 : 8;
+	if (smmu->asid_bits < asid_bits)
+		return false;
+
+	/*
+	 * See max_pinned_asids in arch/arm64/mm/context.c. The following is
+	 * generally the maximum number of bindable processes.
+	 */
+	if (IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0))
+		asid_bits--;
+	dev_dbg(smmu->dev, "%d shared contexts\n", (1 << asid_bits) -
+		num_possible_cpus() - 2);
+
+	return true;
+}
+
 static int arm_smmu_device_hw_probe(struct arm_smmu_device *smmu)
 {
 	u32 reg;
@@ -2766,6 +2835,9 @@ static int arm_smmu_device_hw_probe(struct arm_smmu_device *smmu)
 
 	smmu->ias = max(smmu->ias, smmu->oas);
 
+	if (arm_smmu_supports_sva(smmu))
+		smmu->features |= ARM_SMMU_FEAT_SVA;
+
 	dev_info(smmu->dev, "ias %lu-bit, oas %lu-bit (features 0x%08x)\n",
 		 smmu->ias, smmu->oas, smmu->features);
 	return 0;
-- 
2.17.0