[PATCH v9 12/25] iommu/arm-smmu-v3-kvm: Probe SMMU HW

[Mostafa Saleh <smostafa@google.com>]

Probe the SMMU features from the IDR registers with the functions shared
with the kernel driver. SubstreamID bits and queue sizes are not needed
here: CDs are not shadowed and the command queue is set up later.

The hypervisor requires two things the kernel driver does not:
- Coherent table walks, reported by both firmware and IDR0.COHACC, as
  it does no cache maintenance on its tables.
- Nested translation, as the host keeps stage-1 and the hypervisor adds
  stage-2.

Signed-off-by: Mostafa Saleh <smostafa@google.com>
---
 .../arm/arm-smmu-v3/pkvm/arm-smmu-v3-hyp.c    | 46 ++++++++++++++++++-
 1 file changed, 45 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/arm/arm-smmu-v3/pkvm/arm-smmu-v3-hyp.c b/drivers/iommu/arm/arm-smmu-v3/pkvm/arm-smmu-v3-hyp.c
index ba209951039f..2b4a0f961a66 100644
--- a/drivers/iommu/arm/arm-smmu-v3/pkvm/arm-smmu-v3-hyp.c
+++ b/drivers/iommu/arm/arm-smmu-v3/pkvm/arm-smmu-v3-hyp.c
@@ -31,6 +31,47 @@ static void smmu_deinit_device(struct hyp_arm_smmu_v3_device *smmu)
 	smmu->base = NULL;
 }
 
+/*
+ * Mini-probe and validation for the hypervisor.
+ */
+static int smmu_probe(struct hyp_arm_smmu_v3_device *smmu)
+{
+	u32 reg;
+	int ret;
+
+	/* Not supported yet. */
+	if (!(smmu->features & ARM_SMMU_FEAT_COHERENCY))
+		return -ENXIO;
+
+	ret = arm_smmu_device_idr0_probe(smmu, true, &reg);
+	if (ret)
+		return ret;
+
+	/*
+	 * Core code clears FEAT_ATS with !CONFIG_PCI_ATS, but the hypervisor
+	 * must know if it is actually supported for CR0 emulation.
+	 */
+	if (reg & IDR0_ATS)
+		smmu->features |= ARM_SMMU_FEAT_ATS;
+
+	/* Firmware says coherent, the hardware must agree. */
+	if (!(reg & IDR0_COHACC))
+		return -ENXIO;
+
+	ret = arm_smmu_device_idr1_probe(smmu, &reg);
+	if (ret)
+		return ret;
+
+	arm_smmu_device_idr3_probe(smmu);
+	arm_smmu_device_idr5_probe(smmu);
+	arm_smmu_device_iidr_probe(smmu);
+
+	if (!(smmu->features & ARM_SMMU_FEAT_NESTING))
+		return -ENXIO;
+
+	return 0;
+}
+
 static int smmu_init_device(struct hyp_arm_smmu_v3_device *smmu)
 {
 	unsigned long haddr;
@@ -45,8 +86,11 @@ static int smmu_init_device(struct hyp_arm_smmu_v3_device *smmu)
 		return ret;
 
 	smmu->base = (void __iomem *)haddr;
+	ret = smmu_probe(smmu);
+	if (ret)
+		smmu_deinit_device(smmu);
 
-	return 0;
+	return ret;
 }
 
 /* Called while the host is still trusted. */
-- 
2.56.0.176.g3575e65682-goog