Re: [Xen-devel] [PATCH v7 1/2] VT-d: Reduce spin timeout to 1ms, which can be boot-time changed

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

On March 17, 2016 4:14pm, <JBeulich@xxxxxxxx> wrote:
> >>> On 17.03.16 at 09:11, <quan.xu@xxxxxxxxx> wrote:
> > On March 17, 2016 3:45pm, Tian, Kevin <kevin.tian@xxxxxxxxx> wrote:
> >> > From: Xu, Quan
> >> > Sent: Thursday, March 17, 2016 3:13 PM diff --git
> >> > a/xen/drivers/passthrough/vtd/qinval.c
> >> > b/xen/drivers/passthrough/vtd/qinval.c
> >> > index b81b0bd..37a15fb 100644
> >> > --- a/xen/drivers/passthrough/vtd/qinval.c
> >> > +++ b/xen/drivers/passthrough/vtd/qinval.c
> >> > @@ -28,6 +28,11 @@
> >> >  #include "vtd.h"
> >> >  #include "extern.h"
> >> >
> >> > +static unsigned int __read_mostly vtd_qi_timeout = 1;
> >> > +integer_param("vtd_qi_timeout", vtd_qi_timeout);
> >> > +
> >> > +#define IOMMU_QI_TIMEOUT (vtd_qi_timeout * MILLISECS(1))
> >> > +
> >> >  static void print_qi_regs(struct iommu *iommu)  {
> >> >      u64 val;
> >> > @@ -130,10 +135,14 @@ static void queue_invalidate_iotlb(struct
> >> > iommu
> >> *iommu,
> >> >      spin_unlock_irqrestore(&iommu->register_lock, flags);  }
> >> >
> >> > +/*
> >> > + * NB. We must check all kinds of error and all the way up the
> >> > + * call trees.
> >> > + */
> >>
> >> This comment is meaningless put in the code. It just reflects what
> >> you need
> > do
> >> to push the whole patch series, but it's obvious a straightforward
> > requirement.
> >>
> > Kevin,
> > This is for Jan requirement:
> >
> > http://lists.xenproject.org/archives/html/xen-devel/2016-02/msg02388.h
> > tml
> > Jan said:
> > """ Without a __must_check annotation on the function I cannot see how
> > I should reasonably convince myself that all call sites now handle
> > such an error in one way or another."""
> >
> > Now I think I misunderstood what Jan said. It may be:
> >
> > + static int __must_check queue_invalidate_wait(struct iommu *iommu,
> > + u8
> > iflag, u8 sw, u8 fn)
> >
> > I found that there is a '__must_check' in xen code.
> 
> Indeed that's what I meant.
> 
Sorry:(.. I will fix it next v8.
Quan

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