[PATCH v2] iommu/amd: Add support for hw_info for iommu capability query

[PATCH v2] 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 passes the raw value of amd_iommu_efr and
amd_iommu_efr2 to VMM via iommufd IOMMU_DEVICE_GET_HW_INFO ioctl.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
---
Change in v2:
 * Do not mask the EFR/EFR2 and simply return the value reported by hardware
 * Move amd_iommufd_hw_info() to drivers/iommu/amd/iommufd.c
 * Also support IOMMU_HW_INFO_TYPE_DEFAULT

 drivers/iommu/amd/Makefile   |  2 +-
 drivers/iommu/amd/iommu.c    |  2 ++
 drivers/iommu/amd/iommufd.c  | 34 ++++++++++++++++++++++++++++++++++
 drivers/iommu/amd/iommufd.h  | 11 +++++++++++
 include/uapi/linux/iommufd.h | 19 +++++++++++++++++++
 5 files changed, 67 insertions(+), 1 deletion(-)
 create mode 100644 drivers/iommu/amd/iommufd.c
 create mode 100644 drivers/iommu/amd/iommufd.h

diff --git a/drivers/iommu/amd/Makefile b/drivers/iommu/amd/Makefile
index 59c04a67f398..b74384465594 100644
--- a/drivers/iommu/amd/Makefile
+++ b/drivers/iommu/amd/Makefile
@@ -1,3 +1,3 @@
 # SPDX-License-Identifier: GPL-2.0-only
-obj-y += iommu.o init.o quirks.o io_pgtable.o io_pgtable_v2.o ppr.o pasid.o
+obj-y += iommu.o init.o quirks.o io_pgtable.o io_pgtable_v2.o ppr.o pasid.o iommufd.o
 obj-$(CONFIG_AMD_IOMMU_DEBUGFS) += debugfs.o
diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index eb348c63a8d0..344364ef94f8 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -42,6 +42,7 @@
 #include <uapi/linux/iommufd.h>
 
 #include "amd_iommu.h"
+#include "iommufd.h"
 #include "../dma-iommu.h"
 #include "../irq_remapping.h"
 #include "../iommu-pages.h"
@@ -3040,6 +3041,7 @@ static const struct iommu_dirty_ops amd_dirty_ops = {
 
 const struct iommu_ops amd_iommu_ops = {
 	.capable = amd_iommu_capable,
+	.hw_info = amd_iommufd_hw_info,
 	.blocked_domain = &blocked_domain,
 	.release_domain = &release_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..08deccf9d35a
--- /dev/null
+++ b/drivers/iommu/amd/iommufd.c
@@ -0,0 +1,34 @@
+// 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;
+
+	pr_debug("%s: efr=%#llx, efr2=%#llx\n", __func__,
+		 hwinfo->efr, hwinfo->efr2);
+
+	return hwinfo;
+}
diff --git a/drivers/iommu/amd/iommufd.h b/drivers/iommu/amd/iommufd.h
new file mode 100644
index 000000000000..7c30dcc66a59
--- /dev/null
+++ b/drivers/iommu/amd/iommufd.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2025 Advanced Micro Devices, Inc.
+ */
+
+#ifndef AMD_IOMMUFD_H
+#define AMD_IOMMUFD_H
+
+extern void *amd_iommufd_hw_info(struct device *dev, u32 *length, u32 *type);
+
+#endif /* AMD_IOMMUFD_H */
diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
index c218c89e0e2e..1adbcc89eccf 100644
--- a/include/uapi/linux/iommufd.h
+++ b/include/uapi/linux/iommufd.h
@@ -613,6 +613,24 @@ 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) reported by hardware
+ * @efr2: Value of AMD IOMMU Extended Feature 2 Register (EFR2) reported by hardware
+ *
+ * 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: Output by the drivers that do not report hardware
@@ -629,6 +647,7 @@ 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

Re: [PATCH v2] iommu/amd: Add support for hw_info for iommu capability query

[Nicolin Chen]

On Wed, Aug 27, 2025 at 02:22:50PM +0000, Suravee Suthikulpanit wrote:
> 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.
> 
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>

Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>

With some nits:

> diff --git a/drivers/iommu/amd/iommufd.h b/drivers/iommu/amd/iommufd.h
> new file mode 100644
> index 000000000000..7c30dcc66a59
> --- /dev/null
> +++ b/drivers/iommu/amd/iommufd.h
> @@ -0,0 +1,11 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2025 Advanced Micro Devices, Inc.
> + */
> +
> +#ifndef AMD_IOMMUFD_H
> +#define AMD_IOMMUFD_H
> +
> +extern void *amd_iommufd_hw_info(struct device *dev, u32 *length, u32 *type);

No need of "extern"?

> +/**
> + * struct iommu_hw_info_amd - AMD IOMMU device info
> + *
> + * @efr : Value of AMD IOMMU Extended Feature Register (EFR) reported by hardware
> + * @efr2: Value of AMD IOMMU Extended Feature 2 Register (EFR2) reported by hardware
> + *
> + * 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)

The link gives me:

404: Page Not Found
Sorry, we couldn’t find that page.

:-/

>  /**
>   * enum iommu_hw_info_type - IOMMU Hardware Info Types
>   * @IOMMU_HW_INFO_TYPE_NONE: Output by the drivers that do not report hardware
> @@ -629,6 +647,7 @@ 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,

Missing an update in the kdoc above.

Nicolin

Re: [PATCH v2] iommu/amd: Add support for hw_info for iommu capability query

[Suthikulpanit, Suravee]

On 8/27/2025 10:47 AM, Nicolin Chen wrote:
> On Wed, Aug 27, 2025 at 02:22:50PM +0000, Suravee Suthikulpanit wrote:
>> 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.
>>
>> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
> 
> Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
> 
> With some nits:
> 
>> diff --git a/drivers/iommu/amd/iommufd.h b/drivers/iommu/amd/iommufd.h
>> new file mode 100644
>> index 000000000000..7c30dcc66a59
>> --- /dev/null
>> +++ b/drivers/iommu/amd/iommufd.h
>> @@ -0,0 +1,11 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only */
>> +/*
>> + * Copyright (C) 2025 Advanced Micro Devices, Inc.
>> + */
>> +
>> +#ifndef AMD_IOMMUFD_H
>> +#define AMD_IOMMUFD_H
>> +
>> +extern void *amd_iommufd_hw_info(struct device *dev, u32 *length, u32 *type);
> 
> No need of "extern"?

Ok

>> +/**
>> + * struct iommu_hw_info_amd - AMD IOMMU device info
>> + *
>> + * @efr : Value of AMD IOMMU Extended Feature Register (EFR) reported by hardware
>> + * @efr2: Value of AMD IOMMU Extended Feature 2 Register (EFR2) reported by hardware
>> + *
>> + * 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)
> 
> The link gives me:
> 
> 404: Page Not Found
> Sorry, we couldn’t find that page.
> 
> :-/

Ah they just update the link recently. I will include a new one.

>>   /**
>>    * enum iommu_hw_info_type - IOMMU Hardware Info Types
>>    * @IOMMU_HW_INFO_TYPE_NONE: Output by the drivers that do not report hardware
>> @@ -629,6 +647,7 @@ 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,
> 
> Missing an update in the kdoc above.

Fixed.

I will update and send out v3 soon.

Thank you,
Suravee