[PATCH v6 01/13] iommu/amd: Add support for hw_info for iommu capability query

Suravee Suthikulpanit
2026-01-15T06:08:47Z

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 passes the raw value of amd_iommu_efr and
amd_iommu_efr2 to VMM via iommufd IOMMU_DEVICE_GET_HW_INFO ioctl.

Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
---
drivers/iommu/amd/Kconfig | 10 ++++++++++
drivers/iommu/amd/Makefile | 1 +
drivers/iommu/amd/iommu.c | 2 ++
drivers/iommu/amd/iommufd.c | 31 +++++++++++++++++++++++++++++++
drivers/iommu/amd/iommufd.h | 15 +++++++++++++++
include/uapi/linux/iommufd.h | 28 ++++++++++++++++++++++++++++
6 files changed, 87 insertions(+)
create mode 100644 drivers/iommu/amd/iommufd.c
create mode 100644 drivers/iommu/amd/iommufd.h

diff --git a/drivers/iommu/amd/Kconfig b/drivers/iommu/amd/Kconfig
index f2acf471cb5d..588355ff7eb7 100644
--- a/drivers/iommu/amd/Kconfig
+++ b/drivers/iommu/amd/Kconfig
@@ -30,6 +30,16 @@ config AMD_IOMMU
your BIOS for an option to enable it or if you have an IVRS ACPI
table.

+config AMD_IOMMU_IOMMUFD
+ bool "Enable IOMMUFD features for AMD IOMMU (EXPERIMENTAL)"
+ depends on IOMMUFD
+ depends on AMD_IOMMU
+ help
+ Support for IOMMUFD features intended to support virtual machines
+ with accelerated virtual IOMMUs.
+
+ Say Y here if you are doing development and testing on this feature.
+
config AMD_IOMMU_DEBUGFS
bool "Enable AMD IOMMU internals in DebugFS"
depends on AMD_IOMMU && IOMMU_DEBUGFS
diff --git a/drivers/iommu/amd/Makefile b/drivers/iommu/amd/Makefile
index 5412a563c697..41f053b49dce 100644
--- a/drivers/iommu/amd/Makefile
+++ b/drivers/iommu/amd/Makefile
@@ -1,3 +1,4 @@
# SPDX-License-Identifier: GPL-2.0-only
obj-y += iommu.o init.o quirks.o ppr.o pasid.o
+obj-$(CONFIG_AMD_IOMMU_IOMMUFD) += iommufd.o
obj-$(CONFIG_AMD_IOMMU_DEBUGFS) += debugfs.o
diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index 5d45795c367a..b6154c73e514 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -43,6 +43,7 @@
#include <linux/generic_pt/iommu.h>

#include "amd_iommu.h"
+#include "iommufd.h"
#include "../irq_remapping.h"
#include "../iommu-pages.h"

@@ -3079,6 +3080,7 @@ static bool amd_iommu_enforce_cache_coherency(struct iommu_domain *domain)

const struct iommu_ops amd_iommu_ops = {
.capable = amd_iommu_capable,
+ .hw_info = amd_iommufd_hw_info,
.blocked_domain = &blocked_domain,
.release_domain = &blocked_domain,
.identity_domain = &identity_domain.domain,
diff --git a/drivers/iommu/amd/iommufd.c b/drivers/iommu/amd/iommufd.c
new file mode 100644
index 000000000000..72eaaa923d04
--- /dev/null
+++ b/drivers/iommu/amd/iommufd.c
@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2025 Advanced Micro Devices, Inc.
+ */
+
+#include <linux/iommu.h>
+
+#include "iommufd.h"
+#include "amd_iommu.h"
+#include "amd_iommu_types.h"
+
+void *amd_iommufd_hw_info(struct device *dev, u32 *length, u32 *type)
+{
+ struct iommu_hw_info_amd *hwinfo;
+
+ if (*type != IOMMU_HW_INFO_TYPE_DEFAULT &&
+ *type != IOMMU_HW_INFO_TYPE_AMD)
+ return ERR_PTR(-EOPNOTSUPP);
+
+ hwinfo = kzalloc(sizeof(*hwinfo), GFP_KERNEL);
+ if (!hwinfo)
+ return ERR_PTR(-ENOMEM);
+
+ *length = sizeof(*hwinfo);
+ *type = IOMMU_HW_INFO_TYPE_AMD;
+
+ hwinfo->efr = amd_iommu_efr;
+ hwinfo->efr2 = amd_iommu_efr2;
+
+ return hwinfo;
+}
diff --git a/drivers/iommu/amd/iommufd.h b/drivers/iommu/amd/iommufd.h
new file mode 100644
index 000000000000..f880be80a30d
--- /dev/null
+++ b/drivers/iommu/amd/iommufd.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2025 Advanced Micro Devices, Inc.
+ */
+
+#ifndef AMD_IOMMUFD_H
+#define AMD_IOMMUFD_H
+
+#if IS_ENABLED(CONFIG_AMD_IOMMU_IOMMUFD)
+void *amd_iommufd_hw_info(struct device *dev, u32 *length, u32 *type);
+#else
+#define amd_iommufd_hw_info NULL
+#endif /* CONFIG_AMD_IOMMU_IOMMUFD */
+
+#endif /* AMD_IOMMUFD_H */
diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
index 2c41920b641d..3db37f6042a0 100644
--- a/include/uapi/linux/iommufd.h
+++ b/include/uapi/linux/iommufd.h
@@ -623,6 +623,32 @@ struct iommu_hw_info_tegra241_cmdqv {
__u8 __reserved;
};

+/**
+ * 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://docs.amd.com/v/u/en-US/48882_3.10_PUB)
+ *
+ * - MMIO Offset 0030h IOMMU Extended Feature Register
+ * - MMIO Offset 01A0h IOMMU Extended Feature 2 Register
+ *
+ * Note: The EFR and EFR2 are raw values reported by hardware.
+ * VMM is responsible to determine the appropriate flags to be exposed to
+ * the VM since cetertain features are not currently supported by the kernel
+ * for HW-vIOMMU.
+ *
+ * Current VMM-allowed list of feature flags are:
+ * - EFR[GTSup, GASup, GioSup, PPRSup, EPHSup, GATS, GLX, PASmax]
+ */
+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: Output by the drivers that do not report hardware
@@ -632,6 +658,7 @@ struct iommu_hw_info_tegra241_cmdqv {
* @IOMMU_HW_INFO_TYPE_ARM_SMMUV3: ARM SMMUv3 iommu info type
* @IOMMU_HW_INFO_TYPE_TEGRA241_CMDQV: NVIDIA Tegra241 CMDQV (extension for ARM
* SMMUv3) info type
+ * @IOMMU_HW_INFO_TYPE_AMD: AMD IOMMU info type
*/
enum iommu_hw_info_type {
IOMMU_HW_INFO_TYPE_NONE = 0,
@@ -639,6 +666,7 @@ enum iommu_hw_info_type {
IOMMU_HW_INFO_TYPE_INTEL_VTD = 1,
IOMMU_HW_INFO_TYPE_ARM_SMMUV3 = 2,
IOMMU_HW_INFO_TYPE_TEGRA241_CMDQV = 3,
+ IOMMU_HW_INFO_TYPE_AMD = 4,
};

/**
--
2.34.1