[RFC PATCH 36/45] iommu/arm-smmu-v3-kvm: Validate device features

[Jean-Philippe Brucker]

The KVM hypervisor driver supports a small subset of features. Ensure
the implementation is compatible, and disable some unused features.

Signed-off-by: Jean-Philippe Brucker <jean-philippe at linaro.org>
---
 .../iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c   | 57 +++++++++++++++++++
 1 file changed, 57 insertions(+)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c
index 1e0daf9ea4ac..2cc632f6b256 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-kvm.c
@@ -23,6 +23,59 @@ static size_t				kvm_arm_smmu_cur;
 static size_t				kvm_arm_smmu_count;
 static struct hyp_arm_smmu_v3_device	*kvm_arm_smmu_array;
 
+static bool kvm_arm_smmu_validate_features(struct arm_smmu_device *smmu)
+{
+	unsigned long oas;
+	unsigned int required_features =
+		ARM_SMMU_FEAT_TRANS_S2 |
+		ARM_SMMU_FEAT_TT_LE;
+	unsigned int forbidden_features =
+		ARM_SMMU_FEAT_STALL_FORCE;
+	unsigned int keep_features =
+		ARM_SMMU_FEAT_2_LVL_STRTAB	|
+		ARM_SMMU_FEAT_2_LVL_CDTAB	|
+		ARM_SMMU_FEAT_TT_LE		|
+		ARM_SMMU_FEAT_SEV		|
+		ARM_SMMU_FEAT_COHERENCY		|
+		ARM_SMMU_FEAT_TRANS_S1		|
+		ARM_SMMU_FEAT_TRANS_S2		|
+		ARM_SMMU_FEAT_VAX		|
+		ARM_SMMU_FEAT_RANGE_INV;
+
+	if (smmu->options & ARM_SMMU_OPT_PAGE0_REGS_ONLY) {
+		dev_err(smmu->dev, "unsupported layout\n");
+		return false;
+	}
+
+	if ((smmu->features & required_features) != required_features) {
+		dev_err(smmu->dev, "missing features 0x%x\n",
+			required_features & ~smmu->features);
+		return false;
+	}
+
+	if (smmu->features & forbidden_features) {
+		dev_err(smmu->dev, "features 0x%x forbidden\n",
+			smmu->features & forbidden_features);
+		return false;
+	}
+
+	smmu->features &= keep_features;
+
+	/*
+	 * This can be relaxed (although the spec says that OAS "must match
+	 * the system physical address size."), but requires some changes. All
+	 * table and queue allocations must use GFP_DMA* to ensure the SMMU can
+	 * access them.
+	 */
+	oas = get_kvm_ipa_limit();
+	if (smmu->oas < oas) {
+		dev_err(smmu->dev, "incompatible address size\n");
+		return false;
+	}
+
+	return true;
+}
+
 static int kvm_arm_smmu_probe(struct platform_device *pdev)
 {
 	int ret;
@@ -68,11 +121,15 @@ static int kvm_arm_smmu_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	if (!kvm_arm_smmu_validate_features(smmu))
+		return -ENODEV;
+
 	platform_set_drvdata(pdev, host_smmu);
 
 	/* Hypervisor parameters */
 	hyp_smmu->mmio_addr = ioaddr;
 	hyp_smmu->mmio_size = size;
+	hyp_smmu->features = smmu->features;
 	kvm_arm_smmu_cur++;
 
 	return 0;
-- 
2.39.0