linux-kernel - Re: [PATCH v2 3/3] doc: Add ABI documentation for uio_pci

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Message-ID: <2025092538-spokesman-disparity-1aca@gregkh>
Date: Thu, 25 Sep 2025 14:32:19 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Yaxing Guo <guoyaxing@...c.ac.cn>
Cc: linux-kernel@...r.kernel.org, wangran@...c.ac.cn, zhangjian@...c.ac.cn,
	anxu@...c.ac.cn
Subject: Re: [PATCH v2 3/3] doc: Add ABI documentation for uio_pci_sva driver
 sysfs attributes

On Thu, Sep 25, 2025 at 06:40:18PM +0800, Yaxing Guo wrote:
> Add ABI documentation for the sysfs interface provided by the
> uio_pci_sva driver, specifically the 'pasid' attribute.
> 
> The 'pasid' attribute exposes the Process Address Space ID (PASID)
> assigned by the IOMMU to the device for use with Shared Virtual
> Addressing (SVA). User-space UIO applications read this attribute
> to obtain the PASID and program it into the device's configuration
> registers, enabling the device to perform DMA using user-space
> virtual addresses.
> 
> This attribute appears under:
> /sys/bus/pci/drivers/uio_pci_sva/<pci_dev>/pasid
> 
> Signed-off-by: Yaxing Guo <guoyaxing@...c.ac.cn>
> ---
>  .../ABI/testing/sysfs-driver-uio_pci_sva-pasid    | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-driver-uio_pci_sva-pasid
> 
> diff --git a/Documentation/ABI/testing/sysfs-driver-uio_pci_sva-pasid b/Documentation/ABI/testing/sysfs-driver-uio_pci_sva-pasid
> new file mode 100644
> index 000000000000..a6afa8c2775c
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-driver-uio_pci_sva-pasid
> @@ -0,0 +1,15 @@
> +What:		/sys/bus/pci/drivers/uio_pci_sva/<pci_dev>/pasid
> +Date:		September 2025
> +Contact:	Yaxing Guo <guoyaxing@...c.ac.cn>
> +Description:
> +		Process Address Space ID (PASID) assigned by IOMMU driver to
> +		the device for use witch Shared Virtual Addressing (SVA).

"with", not "witch", right?

> +
> +		This read-only attribute exposes the PASID allocated by the
> +		IOMMU driver during sva device binding.
> +
> +		User-space UIO applications must read this attribute to
> +		obtain the PASID and program it into the device's configuration
> +		registers. This enables the device to perform DMA using
> +		user-space virtual address, with address translation handled
> +		by IOMMU.

What is a PASID?  What format is it in?

How can it then be used in userspace?  What is a "device configuration
register" and what api uses it?

And where is the userspace code that interacts with all of this?

And finally, this too can be part of the first commit.

thanks,

greg k-h