RE: [PATCH v2] arm64: mm: reserve hugetlb CMA after numa_init

[Song Bao Hua (Barry Song)]

> -----Original Message-----
> From: Will Deacon [mailto:will@xxxxxxxxxx]
> Sent: Wednesday, June 17, 2020 10:18 PM
> To: Song Bao Hua (Barry Song) <song.bao.hua@xxxxxxxxxxxxx>
> Cc: catalin.marinas@xxxxxxx; nsaenzjulienne@xxxxxxx;
> steve.capper@xxxxxxx; rppt@xxxxxxxxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx;
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Linuxarm
> <linuxarm@xxxxxxxxxx>; Matthias Brugger <matthias.bgg@xxxxxxxxx>;
> Roman Gushchin <guro@xxxxxx>
> Subject: Re: [PATCH v2] arm64: mm: reserve hugetlb CMA after numa_init
> 
> On Wed, Jun 17, 2020 at 10:19:24AM +1200, Barry Song wrote:
> > hugetlb_cma_reserve() is called at the wrong place. numa_init has not been
> > done yet. so all reserved memory will be located at node0.
> >
> > Fixes: cf11e85fc08c ("mm: hugetlb: optionally allocate gigantic hugepages
> using cma")
> 
> Damn, wasn't CC'd on that :/
> 
> > Cc: Matthias Brugger <matthias.bgg@xxxxxxxxx>
> > Acked-by: Roman Gushchin <guro@xxxxxx>
> > Signed-off-by: Barry Song <song.bao.hua@xxxxxxxxxxxxx>
> > ---
> >  -v2: add Fixes tag according to Matthias Brugger's comment
> >
> >  arch/arm64/mm/init.c | 10 +++++-----
> >  1 file changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> > index e631e6425165..41914b483d54 100644
> > --- a/arch/arm64/mm/init.c
> > +++ b/arch/arm64/mm/init.c
> > @@ -404,11 +404,6 @@ void __init arm64_memblock_init(void)
> >  	high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
> >
> >  	dma_contiguous_reserve(arm64_dma32_phys_limit);
> > -
> > -#ifdef CONFIG_ARM64_4K_PAGES
> > -	hugetlb_cma_reserve(PUD_SHIFT - PAGE_SHIFT);
> > -#endif
> 
> Why is this dependent on CONFIG_ARM64_4K_PAGES? We unconditionally
> select ARCH_HAS_GIGANTIC_PAGE so this seems unnecessary.

Roman, would you like to answer this question? Have you found any problem if system
doesn't set 4K_PAGES?

> 
> > -
> >  }
> >
> >  void __init bootmem_init(void)
> > @@ -424,6 +419,11 @@ void __init bootmem_init(void)
> >  	min_low_pfn = min;
> >
> >  	arm64_numa_init();
> > +
> > +#ifdef CONFIG_ARM64_4K_PAGES
> > +	hugetlb_cma_reserve(PUD_SHIFT - PAGE_SHIFT);
> > +#endif
> 
> A comment here wouldn't hurt, as it does look a lot more natural next
> to dma_contiguous_reserve().

Will add some comment here.

> 
> Will

barry