Re: [Xen-devel] [PATCH] xen/mm: Alter is_iomem_page() to use mfn_t

[David Woodhouse <dwmw2@xxxxxxxxxxxxx>]

On Thu, 2017-02-09 at 01:56 -0700, Jan Beulich wrote:
> 
> > diff --git a/xen/arch/x86/hvm/mtrr.c b/xen/arch/x86/hvm/mtrr.c
> > index 86c71be..3d9386a 100644
> > --- a/xen/arch/x86/hvm/mtrr.c
> > +++ b/xen/arch/x86/hvm/mtrr.c
> > @@ -784,6 +784,8 @@ int epte_get_entry_emt(struct domain *d, unsigned long 
> > gfn, 
> >  
> >      if ( direct_mmio )
> >      {
> > +        ASSERT(direct_mmio == is_iomem_page(mfn)); 
> > +
> >          if ( (mfn_x(mfn) ^ d->arch.hvm_domain.vmx.apic_access_mfn) >> 
> >order )
> >              return MTRR_TYPE_UNCACHABLE;
> >          if ( order )
> > 
> > But when I try to create a hvm domain, it failed. logs are below.
> 
> Considering the context of the change above, I'm not surprised:
> You've very likely hit the APIC access MFN.

You'll probably hit it for INVALID_MFN too on an unmap. And *do* make
it print the offending address when it triggers. :)

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