Re: [PATCH makedumpfile] Align PMD_SECTION_MASK with PHYS_MASK

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On Tue, Mar 17, 2020 at 02:14:22PM +0000, HAGIO KAZUHITO(萩尾 一仁) wrote:
> Hi Michal,
> 
> Thank you for the patch.
> 
> > -----Original Message-----
> > Reportedly on some arm64 systems makedumpfile loops forever exhausting
> > all memory when filtering kernel core. It turns out the reason is it
> > cannot resolve some addresses because the PMD mask is wrong. When
> > physical address mask allows up to 48bits pmd mask should allow the
> > same.
> > I suppose you would need a system that needs physical addresses over 1TB
> > to be able to reproduce this. This may be either because you have a lot
> > of memory or because the firmware mapped some memory above 1TB for some
> > reason.
> > 
> > Signed-off-by: Michal Suchanek <msuchanek@xxxxxxx>
> > ---
> >  arch/arm64.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm64.c b/arch/arm64.c
> > index 43164ccc32d4..54d60b440850 100644
> > --- a/arch/arm64.c
> > +++ b/arch/arm64.c
> > @@ -81,7 +81,7 @@ static unsigned long kimage_voffset;
> >   * Remove the highest order bits that are not a part of the
> >   * physical address in a section
> >   */
> > -#define PMD_SECTION_MASK	((1UL << 40) - 1)
> > +#define PMD_SECTION_MASK	((1UL << PHYS_MASK_SHIFT) - 1)
> > 
> >  #define PMD_TYPE_MASK		3
> >  #define PMD_TYPE_SECT		1
> > --
> > 2.23.0
> > 
> 
> Then I'd prefer to remove PMD_SECTION_MASK and use PHYS_MASK instead.
> Is it OK?  Keeping PMD_SECTION_MASK looks a little confusing to me.

This code will need to be changed for 52bit support. It remains to be
seen if the mask will be still the same after that. I would go with just
the minimal fix for now to not complicate things.

Thanks

Michal

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