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

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

On March 17, 2016 3:45pm, Tian, Kevin <kevin.tian@intel.com> 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.html
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.

Quan


> >  static int queue_invalidate_wait(struct iommu *iommu,
> >      u8 iflag, u8 sw, u8 fn)
> >  {





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