linux-kernel - Re: [PATCH v6 17/25] iommufd: Allow an input data_type via iommu_hw

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Message-ID: <20250616141457.GH1174925@nvidia.com>
Date: Mon, 16 Jun 2025 11:14:57 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: kevin.tian@...el.com, corbet@....net, will@...nel.org,
	bagasdotme@...il.com, robin.murphy@....com, joro@...tes.org,
	thierry.reding@...il.com, vdumpa@...dia.com, jonathanh@...dia.com,
	shuah@...nel.org, jsnitsel@...hat.com, nathan@...nel.org,
	peterz@...radead.org, yi.l.liu@...el.com, mshavit@...gle.com,
	praan@...gle.com, zhangzekun11@...wei.com, iommu@...ts.linux.dev,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-tegra@...r.kernel.org,
	linux-kselftest@...r.kernel.org, patches@...ts.linux.dev,
	mochs@...dia.com, alok.a.tiwari@...cle.com, vasant.hegde@....com,
	dwmw2@...radead.org, baolu.lu@...ux.intel.com
Subject: Re: [PATCH v6 17/25] iommufd: Allow an input data_type via
 iommu_hw_info

On Sat, Jun 14, 2025 at 12:14:42AM -0700, Nicolin Chen wrote:
> The iommu_hw_info can output via the out_data_type field the vendor data
> type from a driver, but this only allows driver to report one data type.
> 
> Now, with SMMUv3 having a Tegra241 CMDQV implementation, it has two sets
> of types and data structs to report.
> 
> One way to support that is to use the same type field bidirectionally.
> 
> Reuse the same field by adding an "in_data_type", allowing user space to
> request for a specific type and to get the corresponding data.
> 
> For backward compatibility, since the ioctl handler has never checked an
> input value, add an IOMMU_HW_INFO_FLAG_INPUT_TYPE to switch between the
> old output-only field and the new bidirectional field.
> 
> Reviewed-by: Kevin Tian <kevin.tian@...el.com>
> Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
> ---
>  include/uapi/linux/iommufd.h   | 20 +++++++++++++++++++-
>  drivers/iommu/iommufd/device.c |  9 ++++++---
>  2 files changed, 25 insertions(+), 4 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

Jason