Re: [Xen-devel] [PATCH] x86/pvh: fix PVHv2 Dom0 memory calculation

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

On Wed, Sep 27, 2017 at 02:26:37PM +0000, Jan Beulich wrote:
> >>> On 27.09.17 at 16:16, <roger.pau@xxxxxxxxxx> wrote:
> > --- a/xen/arch/x86/dom0_build.c
> > +++ b/xen/arch/x86/dom0_build.c
> > @@ -263,8 +263,7 @@ unsigned long __init dom0_compute_nr_pages(
> >              avail -= max_pdx >> s;
> >      }
> >  
> > -    need_paging = is_hvm_domain(d) &&
> > -        (!iommu_hap_pt_share || !paging_mode_hap(d));
> > +    need_paging = is_hvm_domain(d);
> >      for ( ; ; need_paging = false )
> >      {
> >          nr_pages = dom0_nrpages;
> 
> Still in context above is the calculation for IOMMU page tables
> When iommu_hap_pt_share, why do we need to reserve extra
> space? If the IOMMU calculation isn't precise enough, perhaps
> that's what wants changing? Quite possibly it would suffice to
> simply double the value dom0_paging_pages() returns in that
> case.

I have not seen this issue myself, perhaps Boris can provide a little
more context on how to trigger this, so that the cause can be narrowed
down.

Thanks, Roger.

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