[PATCH] arm64: Use correct method to calculate nomap region boundaries

[Huacai Chen]

Hi, Will

On Thu, Dec 2, 2021 at 6:08 PM Will Deacon <will at kernel.org> wrote:
>
> On Fri, Oct 22, 2021 at 03:06:46PM +0800, Huacai Chen wrote:
> > Nomap regions are treated as "reserved". When region boundaries are not
> > page aligned, we usually increase the "reserved" regions rather than
> > decrease them. So, we should use memblock_region_reserved_base_pfn()/
> > memblock_region_reserved_end_pfn() instead of memblock_region_memory_
> > base_pfn()/memblock_region_memory_base_pfn() to calculate boundaries.
> >
> > Signed-off-by: Huacai Chen <chenhuacai at loongson.cn>
> > ---
> >  arch/arm64/kernel/setup.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> > index be5f85b0a24d..1e86d4c5ef8c 100644
> > --- a/arch/arm64/kernel/setup.c
> > +++ b/arch/arm64/kernel/setup.c
> > @@ -232,12 +232,14 @@ static void __init request_standard_resources(void)
> >               if (memblock_is_nomap(region)) {
> >                       res->name  = "reserved";
> >                       res->flags = IORESOURCE_MEM;
> > +                     res->start = __pfn_to_phys(memblock_region_reserved_base_pfn(region));
> > +                     res->end = __pfn_to_phys(memblock_region_reserved_end_pfn(region)) - 1;
> >               } else {
> >                       res->name  = "System RAM";
> >                       res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
> > +                     res->start = __pfn_to_phys(memblock_region_memory_base_pfn(region));
> > +                     res->end = __pfn_to_phys(memblock_region_memory_end_pfn(region)) - 1;
> >               }
> > -             res->start = __pfn_to_phys(memblock_region_memory_base_pfn(region));
> > -             res->end = __pfn_to_phys(memblock_region_memory_end_pfn(region)) - 1;
>
> Under which circumstances would the nomap regions not be page-aligned? That
> sounds like something we should prevent, rather than work around here.

In this call path:
acpi_table_upgrade --> arch_reserve_mem_area --> memblock_mark_nomap
The nomap region is not page-aligned.

Huacai
>
> Will