Re: [Xen-devel] [PATCH v8 1/3] VT-d: Reduce spin timeout to 1ms, which can be boot-time changed

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

On March 24, 2016 7:04pm, <dario.faggioli@xxxxxxxxxx> wrote:
> On Thu, 2016-03-24 at 13:57 +0800, Quan Xu wrote:
> >
> > --- a/docs/misc/xen-command-line.markdown
> > +++ b/docs/misc/xen-command-line.markdown
> > @@ -1532,6 +1532,13 @@ 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.
> > +
> Perhaps we should put down a quick paragraph to explain what this parameter
> is about, and what happens if the timeout expires?
> 
> Giving hints on under what conditions one should change this value would be
> even more welcome (e.g. "if you see error XXX, try increasing the timeout to
> nnn").
> 
Make sense. I would send out this paragraph before v9. I hope you could help me 
correct it. :)


> > --- a/xen/drivers/passthrough/vtd/qinval.c
> > +++ b/xen/drivers/passthrough/vtd/qinval.c
> >
> > @@ -130,10 +135,10 @@ static void queue_invalidate_iotlb(struct iommu
> >
> > *iommu,
> >      spin_unlock_irqrestore(&iommu->register_lock, flags);
> >  }
> >
> > -static int queue_invalidate_wait(struct iommu *iommu,
> > +static int __must_check queue_invalidate_wait(struct iommu *iommu,
> >      u8 iflag, u8 sw, u8 fn)
> >  {
> >
> I'm not sure it is ok to add the __must_check annotation here in this patch,
> considering that the subject says "VT-d: Reduce spin timeout to 1ms, which can
> be boot-time changed", and there is no changelog.
> 
> Personally, I think it could be ok, but at least add a few words of changelog,
> mentioning that this is also being done.
> 
Thanks for your reminding. It's better to add a few words of changelog.

Quan
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