linux-kernel - Re: [PATCH v2 2/4] memblock: update initialization of reserved pages

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Message-ID: <752fd822-6479-53f1-81fb-24b55500e963@redhat.com>
Date:   Wed, 21 Apr 2021 09:49:24 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Mike Rapoport <rppt@...nel.org>,
        linux-arm-kernel@...ts.infradead.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Catalin Marinas <catalin.marinas@....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: [PATCH v2 2/4] memblock: update initialization of reserved pages

On 21.04.21 08:51, 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.
> 
> Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
> ---
>   include/linux/memblock.h |  4 +++-
>   mm/memblock.c            | 28 ++++++++++++++++++++++++++--
>   2 files changed, 29 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index 5984fff3f175..634c1a578db8 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -30,7 +30,9 @@ extern unsigned long long max_possible_pfn;
>    * @MEMBLOCK_NONE: no special request
>    * @MEMBLOCK_HOTPLUG: hotpluggable region
>    * @MEMBLOCK_MIRROR: mirrored region
> - * @MEMBLOCK_NOMAP: don't add to kernel direct mapping
> + * @MEMBLOCK_NOMAP: don't add to kernel direct mapping and treat as
> + * reserved in the memory map; refer to memblock_mark_nomap() description
> + * for futher details
>    */
>   enum memblock_flags {
>   	MEMBLOCK_NONE		= 0x0,	/* No special request */
> diff --git a/mm/memblock.c b/mm/memblock.c
> index afaefa8fc6ab..3abf2c3fea7f 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -906,6 +906,11 @@ int __init_memblock memblock_mark_mirror(phys_addr_t base, phys_addr_t size)
>    * @base: the base phys addr of the region
>    * @size: the size of the region
>    *
> + * The memory regions marked with %MEMBLOCK_NOMAP will not be added to the
> + * direct mapping of the physical memory. These regions will still be
> + * covered by the memory map. The struct page representing NOMAP memory
> + * frames in the memory map will be PageReserved()
> + *
>    * Return: 0 on success, -errno on failure.
>    */
>   int __init_memblock memblock_mark_nomap(phys_addr_t base, phys_addr_t size)
> @@ -2002,6 +2007,26 @@ 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 +2035,7 @@ 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
> 

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 
Thanks,

David / dhildenb