linux-kernel - Re: [PATCH v3 6/6] dmaengine: idxd: add ABI documentation for shared wq

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Date:   Mon, 6 Jul 2020 11:57:30 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Dave Jiang <dave.jiang@...el.com>, vkoul@...nel.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de
Cc:     Jing Lin <jing.lin@...el.com>, Tony Luck <tony.luck@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        x86@...nel.org, ashok.raj@...el.com, fenghua.yu@...el.com
Subject: Re: [PATCH v3 6/6] dmaengine: idxd: add ABI documentation for shared
 wq

On 7/6/20 11:22 AM, Dave Jiang wrote:
> +What:		/sys/bus/dsa/devices/dsa<m>/pasid_enabled
> +Date:		Jul 5, 2020
> +KernelVersion:	5.9.0
> +Contact:	dmaengine@...r.kernel.org
> +Description:	To indicate if PASID (process address space identifier) is
> +		enabled or not for this device.
> +
>  What:           /sys/bus/dsa/devices/dsa<m>/state
>  Date:           Oct 25, 2019
>  KernelVersion:  5.6.0
> @@ -116,6 +123,13 @@ Description:    The maximum number of bandwidth tokens that may be in use at
>  		one time by operations that access low bandwidth memory in the
>  		device.
>  
> +What:		/sys/bus/dsa/devices/wq<m>.<n>/block_on_fault
> +Date:		Jul 5, 2020
> +KernelVersion:	5.9.0
> +Contact:	dmaengine@...r.kernel.org
> +Description:	To indicate block on fault is allowed or not for the work queue
> +		to support on demand paging.

I'd also really appreciate some more "why" in addition to the "what" in
the documentation.  Why would a program or end user care that PASIDs are
enabled or that on-demand paging is supported?