linux-kernel - Re: [RFC/RFT PATCH 1/3] memblock: update initialization of reserved pages

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Date:   Thu, 8 Apr 2021 08:48:09 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Ard Biesheuvel <ardb@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        David Hildenbrand <david@...hat.com>,
        Marc Zyngier <maz@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Will Deacon <will@...nel.org>, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC/RFT PATCH 1/3] memblock: update initialization of reserved
 pages

On Thu, Apr 08, 2021 at 10:46:18AM +0530, Anshuman Khandual wrote:
> 
> 
> On 4/7/21 10:56 PM, Mike Rapoport wrote:
> > From: Mike Rapoport <rppt@...ux.ibm.com>
> > 
> > The struct pages representing a reserved memory region are initialized
> > using reserve_bootmem_range() function. This function is called for each
> > reserved region just before the memory is freed from memblock to the buddy
> > page allocator.
> > 
> > The struct pages for MEMBLOCK_NOMAP regions are kept with the default
> > values set by the memory map initialization which makes it necessary to
> > have a special treatment for such pages in pfn_valid() and
> > pfn_valid_within().
> > 
> > Split out initialization of the reserved pages to a function with a
> > meaningful name and treat the MEMBLOCK_NOMAP regions the same way as the
> > reserved regions and mark struct pages for the NOMAP regions as
> > PageReserved.
> 
> This would definitely need updating the comment for MEMBLOCK_NOMAP definition
> in include/linux/memblock.h just to make the semantics is clear,

Sure

> though arm64 is currently the only user for MEMBLOCK_NOMAP.

> > Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
> > ---
> >  mm/memblock.c | 23 +++++++++++++++++++++--
> >  1 file changed, 21 insertions(+), 2 deletions(-)
> > 
> > diff --git a/mm/memblock.c b/mm/memblock.c
> > index afaefa8fc6ab..6b7ea9d86310 100644
> > --- a/mm/memblock.c
> > +++ b/mm/memblock.c
> > @@ -2002,6 +2002,26 @@ static unsigned long __init __free_memory_core(phys_addr_t start,
> >  	return end_pfn - start_pfn;
> >  }
> >  
> > +static void __init memmap_init_reserved_pages(void)
> > +{
> > +	struct memblock_region *region;
> > +	phys_addr_t start, end;
> > +	u64 i;
> > +
> > +	/* initialize struct pages for the reserved regions */
> > +	for_each_reserved_mem_range(i, &start, &end)
> > +		reserve_bootmem_region(start, end);
> > +
> > +	/* and also treat struct pages for the NOMAP regions as PageReserved */
> > +	for_each_mem_region(region) {
> > +		if (memblock_is_nomap(region)) {
> > +			start = region->base;
> > +			end = start + region->size;
> > +			reserve_bootmem_region(start, end);
> > +		}
> > +	}
> > +}
> > +
> >  static unsigned long __init free_low_memory_core_early(void)
> >  {
> >  	unsigned long count = 0;
> > @@ -2010,8 +2030,7 @@ static unsigned long __init free_low_memory_core_early(void)
> >  
> >  	memblock_clear_hotplug(0, -1);
> >  
> > -	for_each_reserved_mem_range(i, &start, &end)
> > -		reserve_bootmem_region(start, end);
> > +	memmap_init_reserved_pages();
> >  
> >  	/*
> >  	 * We need to use NUMA_NO_NODE instead of NODE_DATA(0)->node_id
> > 

-- 
Sincerely yours,
Mike.