Re: [Xen-devel] [PATCH v2 4/4] x86/dom0: re-order DMA remapping enabling for PVH Dom0

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

On Tue, Aug 22, 2017 at 06:37:15AM -0600, Jan Beulich wrote:
> >>> On 11.08.17 at 18:43, <roger.pau@xxxxxxxxxx> wrote:
> > Make sure the reserved regions are setup before enabling the DMA
> > remapping in the IOMMU, by calling dom0_setup_permissions before
> > iommu_hwdom_init.
> 
> I can't match up this part with ...
> 
> > --- a/xen/arch/x86/hvm/dom0_build.c
> > +++ b/xen/arch/x86/hvm/dom0_build.c
> > @@ -605,13 +605,6 @@ static int __init pvh_setup_cpus(struct domain *d, 
> > paddr_t entry,
> >          return rc;
> >      }
> >  
> > -    rc = dom0_setup_permissions(d);
> > -    if ( rc )
> > -    {
> > -        panic("Unable to setup Dom0 permissions: %d\n", rc);
> > -        return rc;
> > -    }
> > -
> >      update_domain_wallclock_time(d);
> >  
> >      clear_bit(_VPF_down, &v->pause_flags);
> > @@ -1059,7 +1052,12 @@ int __init dom0_construct_pvh(struct domain *d, 
> > const module_t *image,
> >  
> >      printk("** Building a PVH Dom0 **\n");
> >  
> > -    iommu_hwdom_init(d);
> > +    rc = dom0_setup_permissions(d);
> > +    if ( rc )
> > +    {
> > +        printk("Unable to setup Dom0 permissions: %d\n", rc);
> > +        return rc;
> > +    }
> >  
> >      rc = pvh_setup_p2m(d);
> >      if ( rc )
> > @@ -1068,6 +1066,8 @@ int __init dom0_construct_pvh(struct domain *d, const 
> > module_t *image,
> >          return rc;
> >      }
> >  
> > +    iommu_hwdom_init(d);
> 
> ... you not changing the relative order between these two function
> calls. As to the other half I'm inclined to also wait for better
> understanding of what's going on here, as said in reply to patch 3.

Why not?

dom0_setup_permissions was called from pvh_setup_cpus, while
iommu_hwdom_init was the first function called in
dom0_construct_pvh.

After this patch dom0_setup_permissions is always called before
iommu_hwdom_init.

Roger.

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