[RFC PATCH 2/6] iommu/amd: Add support for hw_info for iommu capability query

[Suravee Suthikulpanit]

AMD IOMMU Extended Feature (EFR) and Extended Feature 2 (EFR2) registers
specify features supported by each IOMMU hardware instance.
The IOMMU driver checks each feature-specific bits before enabling
each feature at run time.

For IOMMUFD, the hypervisor determines which IOMMU features to support
in the guest, and communicates this information to user-space (e.g. QEMU)
via iommufd IOMMU_DEVICE_GET_HW_INFO ioctl.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
---
 drivers/iommu/amd/amd_iommu.h       |  2 ++
 drivers/iommu/amd/amd_iommu_types.h |  3 +++
 drivers/iommu/amd/iommu.c           | 38 +++++++++++++++++++++++++++++
 include/uapi/linux/iommufd.h        | 13 ++++++++++
 4 files changed, 56 insertions(+)

diff --git a/drivers/iommu/amd/amd_iommu.h b/drivers/iommu/amd/amd_iommu.h
index 108253edbeb0..4118129f4a24 100644
--- a/drivers/iommu/amd/amd_iommu.h
+++ b/drivers/iommu/amd/amd_iommu.h
@@ -72,6 +72,8 @@ void amd_iommu_dev_flush_pasid_pages(struct iommu_dev_data *dev_data,
 void amd_iommu_dev_flush_pasid_all(struct iommu_dev_data *dev_data,
 				   ioasid_t pasid);
 
+void amd_iommu_build_efr(u64 *efr, u64 *efr2);
+
 #ifdef CONFIG_IRQ_REMAP
 int amd_iommu_create_irq_domain(struct amd_iommu *iommu);
 #else
diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
index 14f67a8cf755..956fd4658a4a 100644
--- a/drivers/iommu/amd/amd_iommu_types.h
+++ b/drivers/iommu/amd/amd_iommu_types.h
@@ -100,12 +100,15 @@
 #define FEATURE_HDSUP		BIT_ULL(52)
 #define FEATURE_SNP		BIT_ULL(63)
 
+#define FEATURE_GATS_5LEVEL	1ULL
 #define FEATURE_GATS_SHIFT	12
 #define FEATURE_GATS_MASK	(0x03ULL << FEATURE_GATS_SHIFT)
 
+#define FEATURE_GLX_3LEVEL	0ULL
 #define FEATURE_GLX_SHIFT	14
 #define FEATURE_GLX_MASK	(0x03ULL << FEATURE_GLX_SHIFT)
 
+#define FEATURE_PASMAX_16	0xFULL
 #define FEATURE_PASMAX_SHIFT	32
 #define FEATURE_PASMAX_MASK	(0x1FULL << FEATURE_PASMAX_SHIFT)
 
diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index 4e4ff1550cf3..c41932e9f16a 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -2822,8 +2822,46 @@ static const struct iommu_dirty_ops amd_dirty_ops = {
 	.read_and_clear_dirty = amd_iommu_read_and_clear_dirty,
 };
 
+void amd_iommu_build_efr(u64 *efr, u64 *efr2)
+{
+	if (efr) {
+		*efr = (FEATURE_GT | FEATURE_GIOSUP | FEATURE_PPR);
+
+		/* 5-level v2 page table support */
+		*efr |= ((FEATURE_GATS_5LEVEL << FEATURE_GATS_SHIFT) &
+			 FEATURE_GATS_MASK);
+
+		/* 3-level GCR3 table support */
+		*efr |= ((FEATURE_GLX_3LEVEL << FEATURE_GLX_SHIFT) &
+			 FEATURE_GLX_MASK);
+
+		/* 16-bit PASMAX support */
+		*efr |= ((FEATURE_PASMAX_16 << FEATURE_PASMAX_SHIFT) &
+			 FEATURE_PASMAX_MASK);
+	}
+
+	if (efr2)
+		*efr2 = 0;
+}
+
+static void *amd_iommu_hw_info(struct device *dev, u32 *length, u32 *type)
+{
+	struct iommu_hw_info_amd *hwinfo;
+
+	hwinfo = kzalloc(sizeof(*hwinfo), GFP_KERNEL);
+	if (!hwinfo)
+		return ERR_PTR(-ENOMEM);
+
+	*length = sizeof(*hwinfo);
+	*type = IOMMU_HW_INFO_TYPE_AMD;
+
+	amd_iommu_build_efr(&hwinfo->efr, &hwinfo->efr2);
+	return hwinfo;
+}
+
 const struct iommu_ops amd_iommu_ops = {
 	.capable = amd_iommu_capable,
+	.hw_info = amd_iommu_hw_info,
 	.domain_alloc = amd_iommu_domain_alloc,
 	.domain_alloc_user = amd_iommu_domain_alloc_user,
 	.probe_device = amd_iommu_probe_device,
diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
index 0b2bc6252e2c..bf4a1f8ab748 100644
--- a/include/uapi/linux/iommufd.h
+++ b/include/uapi/linux/iommufd.h
@@ -474,15 +474,28 @@ struct iommu_hw_info_vtd {
 	__aligned_u64 ecap_reg;
 };
 
+/**
+ * struct iommu_hw_info_amd - AMD IOMMU device info
+ *
+ * @efr : Value of AMD IOMMU Extended Feature Register (EFR)
+ * @efr2: Value of AMD IOMMU Extended Feature 2 Register (EFR2)
+ */
+struct iommu_hw_info_amd {
+	__u64 efr;
+	__u64 efr2;
+};
+
 /**
  * enum iommu_hw_info_type - IOMMU Hardware Info Types
  * @IOMMU_HW_INFO_TYPE_NONE: Used by the drivers that do not report hardware
  *                           info
  * @IOMMU_HW_INFO_TYPE_INTEL_VTD: Intel VT-d iommu info type
+ * @IOMMU_HW_INFO_TYPE_AMD: AMD IOMMU info type
  */
 enum iommu_hw_info_type {
 	IOMMU_HW_INFO_TYPE_NONE,
 	IOMMU_HW_INFO_TYPE_INTEL_VTD,
+	IOMMU_HW_INFO_TYPE_AMD,
 };
 
 /**
-- 
2.34.1