Re: [Xen-devel] Xen-unstable PVHdom0: Assertion 'IS_ALIGNED(dfn_x(dfn), (1ul << page_order))' failed at iommu.c:324

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

On Fri, Jan 18, 2019 at 03:17:57PM +0100, Sander Eikelenboom wrote:
> On 18/01/2019 13:50, Roger Pau Monné wrote:
> > On Fri, Jan 18, 2019 at 01:03:04PM +0100, Sander Eikelenboom wrote:
> >> Hi Roger,
> >>
> >> I gave PVH dom0 a spin, see how far I would get.
> > 
> > Thanks!
> > 
> >> With current xen-unstable unfortunately not that far, i got the splat 
> >> below.
> > 
> > Yes, this was already reported:
> > 
> > https://lists.xenproject.org/archives/html/xen-devel/2019-01/msg01030.html
> >> If you need more info, would like me to test a patch (or some other git 
> >> tree/branch), 
> >> I will be happy to give it a spin !
> > 
> > Paul is working on a fix, but in the meantime just removing the
> > assertions should be fine:
> > 
> > ---8<---
> > diff --git a/xen/drivers/passthrough/iommu.c 
> > b/xen/drivers/passthrough/iommu.c
> > index bd1af35a13..98e6fc35e2 100644
> > --- a/xen/drivers/passthrough/iommu.c
> > +++ b/xen/drivers/passthrough/iommu.c
> > @@ -321,9 +321,6 @@ int iommu_map(struct domain *d, dfn_t dfn, mfn_t mfn,
> >      if ( !iommu_enabled || !hd->platform_ops )
> >          return 0;
> >  
> > -    ASSERT(IS_ALIGNED(dfn_x(dfn), (1ul << page_order)));
> > -    ASSERT(IS_ALIGNED(mfn_x(mfn), (1ul << page_order)));
> > -
> >      for ( i = 0; i < (1ul << page_order); i++ )
> >      {
> >          rc = hd->platform_ops->map_page(d, dfn_add(dfn, i), mfn_add(mfn, 
> > i),
> > 
> 
> I gave that a spin and i now get a seemingly endless stream of IO_PAGE_FAULTs

You shouldn't get those page faults since they are for addresses that
belong to a reserved region, and that should be mapped into the p2m.
I've just tested on my AMD box and I'm also seeing errors (albeit
different ones), so I guess something broke since I last fixed PVH
Dom0 to boot on AMD hardware.

I've also tested commit:

commit fad6ba64a8c98bebb9374f390cc255fac05237ab (HEAD)
Author: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Date:   Fri Nov 30 12:10:00 2018 +0100
amd/iommu: skip host bridge devices when updating IOMMU page tables

And it works on my AMD box and I'm able to boot as a PVH Dom0. Can you
give this commit a spin?

Thanks, Roger.

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