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

["Jan Beulich" <JBeulich@suse.com>]

>>> On 13.02.19 at 18:13, <roger.pau@citrix.com> wrote:
> On Wed, Feb 13, 2019 at 09:01:07AM -0700, Jan Beulich wrote:
>> >>> On 11.02.19 at 18:46, <roger.pau@citrix.com> 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@citrix.com>
>> 
>> Acked-by: Jan Beulich <jbeulich@suse.com>
>> 
>> 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.

As "a boolean" I think you can use the already present need_paging
one.

Jan


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