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

[Huacai Chen]

Hi, Ren,

On Mon, Nov 1, 2021 at 9:53 AM Guo Ren <guoren at kernel.org> wrote:
>
> The real reserved memory have been initialized before in
> for_each_reserved_mem_region loop. If memblock_is_nomap still uses
> memblock_region_reserved, than it would cause overlap with
> reserved_mem_region.
>
> nomap_region: PFN_DOWN <-> PFN_UP
> reserved_region: PFN_DOWN <-> PFN_UP
>
> We would get overlapped reserved_mem_region.
Nomap regions are subsets of memory regions. And memory regions are
already "decreased" to page-aligned regions. So, nomap regions will
not exceed memory regions and overlap with reserved regions. In fact,
unaligned nomap regions come from memblock_mark_nomap() with unaligned
size.

Huacai
>
> On Wed, Oct 27, 2021 at 4:35 PM Huacai Chen <chenhuacai at gmail.com> wrote:
> >
> > Ping?
> >
> > On Fri, Oct 22, 2021 at 3:07 PM Huacai Chen <chenhuacai at loongson.cn> 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;
> > >
> > >                 request_resource(&iomem_resource, res);
> > >
> > > --
> > > 2.27.0
> > >
>
>
>
> --
> Best Regards
>  Guo Ren
>
> ML: https://lore.kernel.org/linux-csky/