linux-kernel - Re: [PATCH v5] iommu/amd: Add support for hw

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Message-ID: <62bb3eee-588a-40eb-a2c7-739166ac774e@amd.com>
Date: Tue, 21 Oct 2025 09:35:16 -0500
From: "Suthikulpanit, Suravee" <suravee.suthikulpanit@....com>
To: "Tian, Kevin" <kevin.tian@...el.com>, "jgg@...dia.com" <jgg@...dia.com>,
 "nicolinc@...dia.com" <nicolinc@...dia.com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "robin.murphy@....com" <robin.murphy@....com>,
 "will@...nel.org" <will@...nel.org>, "joro@...tes.org" <joro@...tes.org>,
 "jsnitsel@...hat.com" <jsnitsel@...hat.com>,
 "vasant.hegde@....com" <vasant.hegde@....com>,
 "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
 "santosh.shukla@....com" <santosh.shukla@....com>,
 "sairaj.arunkodilkar@....com" <sairaj.arunkodilkar@....com>,
 "jon.grimm@....com" <jon.grimm@....com>,
 "Prakash, Prashanth" <prashanthpra@...gle.com>,
 "wvw@...gle.com" <wvw@...gle.com>, "wnliu@...gle.com" <wnliu@...gle.com>,
 "gptran@...gle.com" <gptran@...gle.com>,
 "kpsingh@...gle.com" <kpsingh@...gle.com>
Subject: Re: [PATCH v5] iommu/amd: Add support for hw_info for iommu
 capability query



On 10/16/2025 2:40 AM, Tian, Kevin wrote:
>> From: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
>> Sent: Friday, September 26, 2025 10:19 PM
>>
>> +/**
>> + * 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.
> 
> this hw_info api should work even w/o HW-vIOMMU?

My understanding is the hw_info API is independent of HW-vIOMMU support. 
It mainly exposes vendor-specific HW capabilities.

Suravee>
> Reviewed-by: Kevin Tian <kevin.tian@...el.com>