Re: [Xen-devel] [PATCH for-4.12 v2 4/7] pvh/dom0: warn when dom0_mem is not set

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

On Wed, Feb 13, 2019 at 09:01:07AM -0700, Jan Beulich wrote:
> >>> On 11.02.19 at 18:46, <roger.pau@xxxxxxxxxx> wrote:
> > There have been several reports of the dom0 builder running out of
> > memory when building a PVH dom0 without having specified a dom0_mem
> > value. Print a warning message if dom0_mem is not set when booting in
> > PVH mode.
> > 
> > This is a temporary workaround until accounting for internal memory
> > required by Xen (ie: paging structures) is improved.
> > 
> > Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> 
> Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> I take it that ...
> 
> > --- a/xen/arch/x86/dom0_build.c
> > +++ b/xen/arch/x86/dom0_build.c
> > @@ -378,8 +378,18 @@ unsigned long __init dom0_compute_nr_pages(
> >           * maximum of 128MB.
> >           */
> >          if ( !nr_pages )
> > +        {
> >              nr_pages = avail - (pv_shim ? pv_shim_mem(avail)
> >                                   : min(avail / 16, 128UL << (20 - 
> > PAGE_SHIFT)));
> > +            if ( is_hvm_domain(d) )
> > +                /*
> > +                 * Temporary workaround message until internal (paging) 
> > memory
> > +                 * accounting required to build a pvh dom0 is improved.
> > +                 */
> > +                printk("WARNING: PVH dom0 without dom0_mem set is still 
> > unstable. "
> > +                       "If you get crashes during boot, try adding a 
> > dom0_mem parameter\n");
> > +        }
> 
> ... you consider it acceptable for the message to be logged twice
> in certain cases?

Right, nr_pages could be set to 0 again if there are 2 iterations of
the parent for loop, in which case using a boolean would be better. I
can fix this in the next version.

Thanks, Roger.

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