Re: [Xen-devel] [PATCH v9 1/3] VT-d: add a command line parameter for Queued Invalidation

["Xu, Quan" <quan.xu@xxxxxxxxx>]

On April 05, 2016 5:09pm, <JBeulich@xxxxxxxx> wrote:
> >>> On 01.04.16 at 16:47, <quan.xu@xxxxxxxxx> wrote:
> 
> The subject should mention "timeout", perhaps either in addition to or in 
> place
> of "command line".
> 

I prefer "VT-d: add a timeout parameter for Queued Invalidation".

> > --- a/docs/misc/xen-command-line.markdown
> > +++ b/docs/misc/xen-command-line.markdown
> > @@ -1532,6 +1532,24 @@ 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 spin timeout is 1ms, which can be boot-time changed.
> 
> Especially the part after the comma makes little sense considering which file
> we're in.

Agreed.

> 
> > +In current code, VT-d Queued Invalidation includes Device-TLB, IOTLB,
> > +Context and IEC flush. If Device-TLB flush timed out, we would hide
> > +the target ATS device and crash the domain owning this ATS device.
> > +If impacted domain is hardware domain, just throw out a warning (done
> > +in queue\_invalidate\_wait). IOTLB, Context and IEC flush timeout are
> > +still in TODO-list.
> 
> Much of this doesn't seem to belong here either.
> 

Could I drop it?

> > +When you see error 'Queue invalidate wait descriptor timed out', try
> > +increasing the vtd\_qi\_timeout to 10ms or more.
> 
> Why 10ms? (If there's no specific reason, I think you'd better drop any 
> explicit
> number.) 

Yes, no specific reason.

Also there's no reason the spell out the command line option again
> here - the context makes clear which value needs increasing.
> 
Agreed.


Then, the new description of xen-command-line.markdown:

+### 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.
+

Any more suggestion?

Quan




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