Re: [Xen-devel] [PATCH v10 1/3] vt-d: add a timeout parameter for Queued Invalidation

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 22.04.16 at 12:54, <quan.xu@xxxxxxxxx> wrote:
> --- a/docs/misc/xen-command-line.markdown
> +++ b/docs/misc/xen-command-line.markdown
> @@ -1532,6 +1532,16 @@ Note that if **watchdog** option is also specified 
> vpmu will be turned off.
>  As the virtualisation is not 100% safe, don't use the vpmu flag on
>  production systems (see http://xenbits.xen.org/xsa/advisory-163.html)! 
>  
> +### vtd\_qi\_timeout (VT-d)
> +> `= <integer>`
> +
> +> Default: `1`
> +
> +Specify the timeout of the VT-d Queued Invalidation in milliseconds.
> +
> +By default, the timeout is 1ms. When you see error 'Queue invalidate wait
> +descriptor timed out', try increasing this value.

So when someone enables ATS, will the 1ms timeout apply to the
dev iotlb invalidations too? If so, that's surely too short, and would
ideally be adjusted automatically, but the need for a higher timeout
in that case should in any event be mentioned here.

Apart from that aspect this patch seems to be ready, but will clearly
need a VT-d maintainer's ack.

Jan


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