iommu/arm-smmu-v3: Check for SVA features

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 SVA, they will have to check
FEAT_STALLS.

Introduce ARM_SMMU_FEAT_BTM (Broadcast TLB Maintenance), but don't
enable it at the moment. Since the entire VMID space is shared with the
CPU, enabling DVM (by clearing SMMU_CR2.PTM) could result in
over-invalidation and affect performance of stage-2 mappings.

Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20200918101852.582559-11-jean-philippe@linaro.org
Signed-off-by: Will Deacon <will@kernel.org>

drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c

@@ -152,3 +152,48 @@ static void arm_smmu_free_shared_cd(struct arm_smmu_ctx_desc *cd)
 		kfree(cd);
 	}
 }
+
+bool arm_smmu_sva_supported(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 (vabits_actual == 52)
+		feat_mask |= ARM_SMMU_FEAT_VAX;
+
+	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. Abort if the MMU outputs
+	 * addresses larger than what we support.
+	 */
+	reg = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1);
+	fld = cpuid_feature_extract_unsigned_field(reg, ID_AA64MMFR0_PARANGE_SHIFT);
+	oas = id_aa64mmfr0_parange_to_phys_shift(fld);
+	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 (arm64_kernel_unmapped_at_el0())
+		asid_bits--;
+	dev_dbg(smmu->dev, "%d shared contexts\n", (1 << asid_bits) -
+		num_possible_cpus() - 2);
+
+	return true;
+}

drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c

@@ -3274,6 +3274,9 @@ static int arm_smmu_device_hw_probe(struct arm_smmu_device *smmu)
 
 	smmu->ias = max(smmu->ias, smmu->oas);
 
+	if (arm_smmu_sva_supported(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;

drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h

@@ -602,6 +602,8 @@ struct arm_smmu_device {
 #define ARM_SMMU_FEAT_STALL_FORCE	(1 << 13)
 #define ARM_SMMU_FEAT_VAX		(1 << 14)
 #define ARM_SMMU_FEAT_RANGE_INV		(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)
@@ -684,4 +686,12 @@ int arm_smmu_write_ctx_desc(struct arm_smmu_domain *smmu_domain, int ssid,
 void arm_smmu_tlb_inv_asid(struct arm_smmu_device *smmu, u16 asid);
 bool arm_smmu_free_asid(struct arm_smmu_ctx_desc *cd);
 
+#ifdef CONFIG_ARM_SMMU_V3_SVA
+bool arm_smmu_sva_supported(struct arm_smmu_device *smmu);
+#else /* CONFIG_ARM_SMMU_V3_SVA */
+static inline bool arm_smmu_sva_supported(struct arm_smmu_device *smmu)
+{
+	return false;
+}
+#endif /* CONFIG_ARM_SMMU_V3_SVA */
 #endif /* _ARM_SMMU_V3_H */