Re: [Xen-devel] [v7][RFC][PATCH 08/13] xen/x86/p2m: set p2m_access_n for reserved device memory mapping

["Chen, Tiejun" <tiejun.chen@xxxxxxxxx>]

On 2014/11/3 18:03, Jan Beulich wrote:
> > > > On 03.11.14 at 10:51, <tiejun.chen@xxxxxxxxx> wrote:
> > On 2014/11/3 17:00, Jan Beulich wrote:
> > > > > > On 03.11.14 at 07:20, <tiejun.chen@xxxxxxxxx> wrote:
> > > > #2 the error handling
> > > >
> > > > In an error case what should I do? Currently we still create these
> > > > mapping as normal. This means these mfns will be valid so later we can't
> > > > set them again then device can't be assigned as passthrough. I think
> > > > this makes sense. Or we should just stop them from setting 1:1 mapping?
> > > You should, with very few exceptions, not ignore errors (which
> > > includes "handling" them by just logging a message. Instead, you
> > > should propagate the error back up the call chain.
> > Do you mean in your patch,
> >
> > +int iommu_get_reserved_device_memory(iommu_grdm_t *func, void *ctxt)
> > +{
> > +    const struct iommu_ops *ops = iommu_get_ops();
> > +
> > +    if ( !iommu_enabled || !ops->get_reserved_device_memory )
> > +        return 0;
> > +
> > +    return ops->get_reserved_device_memory(func, ctxt);
> > +}
> > +
> >
> > I shouldn't return that directly. Then instead, we should handle all
> > error scenarios here?
> No. All error scenarios are already being handled here (by
> propagating the error code to the caller).
Sorry, how to propagate the error code?

Thanks
Tiejun

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