linux-kernel - Re: [PATCH v2] iommu/amd: Add support for hw

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Message-ID: <61483c7d-80d3-4a89-b8e1-8f1263eb1ff0@amd.com>
Date: Wed, 27 Aug 2025 11:22:12 -0500
From: "Suthikulpanit, Suravee" <suravee.suthikulpanit@....com>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: jgg@...dia.com, linux-kernel@...r.kernel.org, robin.murphy@....com,
 will@...nel.org, joro@...tes.org, kevin.tian@...el.com, jsnitsel@...hat.com,
 vasant.hegde@....com, iommu@...ts.linux.dev, santosh.shukla@....com,
 sairaj.arunkodilkar@....com, jon.grimm@....com, prashanthpra@...gle.com,
 wvw@...gle.com, wnliu@...gle.com, gptran@...gle.com, kpsingh@...gle.com
Subject: Re: [PATCH v2] iommu/amd: Add support for hw_info for iommu
 capability query



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