Re: [Xen-devel] [PATCH v4 6/7] xen/arm: don't iomem_permit_access for reserved-memory regions

[Stefano Stabellini <sstabellini@kernel.org>]

On Thu, 8 Aug 2019, Volodymyr Babchuk wrote:
> Hi Stefano,
> 
> Stefano Stabellini writes:
> 
> > Don't allow reserved-memory regions to be remapped into any guests,
> > until reserved-memory regions are properly supported in Xen. For now,
> > do not call iomem_permit_access for them.
> >
> > Signed-off-by: Stefano Stabellini <stefanos@xilinx.com>
> > ---
> >
> > Changes in v4:
> > - compare the parent name with reserved-memory
> > - use dt_node_cmp
> >
> > Changes in v3:
> > - new patch
> > ---
> >  xen/arch/arm/domain_build.c | 24 ++++++++++++++++--------
> >  1 file changed, 16 insertions(+), 8 deletions(-)
> >
> > diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> > index 4c8404155a..267e0549e2 100644
> > --- a/xen/arch/arm/domain_build.c
> > +++ b/xen/arch/arm/domain_build.c
> > @@ -1153,17 +1153,25 @@ static int __init map_range_to_domain(const struct dt_device_node *dev,
> >      struct map_range_data *mr_data = data;
> >      struct domain *d = mr_data->d;
> >      bool need_mapping = !dt_device_for_passthrough(dev);
> > +    const struct dt_device_node *parent = dt_get_parent(dev);
> >      int res;
> >
> > -    res = iomem_permit_access(d, paddr_to_pfn(addr),
> > -                              paddr_to_pfn(PAGE_ALIGN(addr + len - 1)));
> > -    if ( res )
> > +    /*
> > +     * Don't give iomem permissions for reserved-memory ranges until
> > +     * reserved-memory support is complete.
> > +     */
> > +    if ( dt_node_cmp(dt_node_name(parent), "reserved-memory") == 0 )
> Am I missing something, or you are permitting access only if it from a
> "reserved-memory" node? This contradicts with patch description.

Well spotted! I inverted the condition by mistake.


> >      {
> > -        printk(XENLOG_ERR "Unable to permit to dom%d access to"
> > -               " 0x%"PRIx64" - 0x%"PRIx64"\n",
> > -               d->domain_id,
> > -               addr & PAGE_MASK, PAGE_ALIGN(addr + len) - 1);
> > -        return res;
> > +        res = iomem_permit_access(d, paddr_to_pfn(addr),
> > +                                  paddr_to_pfn(PAGE_ALIGN(addr + len - 1)));
> > +        if ( res )
> > +        {
> > +            printk(XENLOG_ERR "Unable to permit to dom%d access to"
> > +                   " 0x%"PRIx64" - 0x%"PRIx64"\n",
> > +                   d->domain_id,
> > +                   addr & PAGE_MASK, PAGE_ALIGN(addr + len) - 1);
> > +            return res;
> > +        }
> >      }
> >
> >      if ( need_mapping )
> So, this region cold be mapped, but without the access?

I'll change it to return early from the function for reserved-memory
regions.

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