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>

1 files changed, 45 insertions, 0 deletions

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
index ef3fcfa72187..cb94c0924196 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c
+++ b/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;
+}