[RFCv2 PATCH 4/7] 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/iommu.c     | 36 +++++++++++++++++++++++++++++++++++
 include/uapi/linux/iommufd.h  | 20 +++++++++++++++++++
 3 files changed, 58 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/iommu.c b/drivers/iommu/amd/iommu.c
index 71099e5fbaee..134f4af921dc 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -2849,8 +2849,44 @@ 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)
+{
+	/* Build the EFR against the current hardware capabilities */
+	if (efr) {
+		*efr = 0ULL;
+		*efr |= (amd_iommu_efr & FEATURE_GT);
+		*efr |= (amd_iommu_efr & FEATURE_GIOSUP);
+		*efr |= (amd_iommu_efr & FEATURE_PPR);
+		*efr |= (amd_iommu_efr & FEATURE_GATS_MASK);
+		*efr |= (amd_iommu_efr & FEATURE_GLX_MASK);
+		*efr |= (amd_iommu_efr & FEATURE_PASMAX_MASK);
+		pr_debug("%s: efr=%#llx\n", __func__, *efr);
+	}
+
+	if (efr2) {
+		*efr2 = 0ULL;
+		pr_debug("%s: efr2=%#llx\n", __func__, *efr);
+	}
+}
+
+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..9901b9f4abe2 100644
--- a/include/uapi/linux/iommufd.h
+++ b/include/uapi/linux/iommufd.h
@@ -474,15 +474,35 @@ 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)
+ *
+ * Please See description of these registers in the following sections of
+ * the AMD I/O Virtualization Technology (IOMMU) Specification.
+ * (https://www.amd.com/content/dam/amd/en/documents/processor-tech-docs/specifications/48882_IOMMU.pdf)
+ *
+ * - MMIO Offset 0030h IOMMU Extended Feature Register
+ * - MMIO Offset 01A0h IOMMU Extended Feature 2 Register
+ */
+struct iommu_hw_info_amd {
+	__aligned_u64 efr;
+	__aligned_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