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Date:   Mon, 13 Jan 2020 09:37:12 +0200
From:   Mike Rapoport <rppt@linux.ibm.com>
To:     Anshuman Khandual <anshuman.khandual@arm.com>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, akpm@linux-foundation.org,
        catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com,
        david@redhat.com, cai@lca.pw, logang@deltatee.com,
        cpandya@codeaurora.org, arunks@codeaurora.org,
        dan.j.williams@intel.com, mgorman@techsingularity.net,
        osalvador@suse.de, ard.biesheuvel@arm.com, steve.capper@arm.com,
        broonie@kernel.org, valentin.schneider@arm.com,
        Robin.Murphy@arm.com, steven.price@arm.com, suzuki.poulose@arm.com,
        ira.weiny@intel.com
Subject: Re: [PATCH V11 2/5] mm/memblock: Introduce MEMBLOCK_BOOT flag
References: <1578625755-11792-1-git-send-email-anshuman.khandual@arm.com>
 <1578625755-11792-3-git-send-email-anshuman.khandual@arm.com>
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On Fri, Jan 10, 2020 at 08:39:12AM +0530, Anshuman Khandual wrote:
> On arm64 platform boot memory should never be hot removed due to certain
> platform specific constraints. Hence the platform would like to override
> earlier added arch call back arch_memory_removable() for this purpose. In
> order to reject boot memory hot removal request, it needs to first track
> them at runtime. In the future, there might be other platforms requiring
> runtime boot memory enumeration. Hence lets expand the existing generic
> memblock framework for this purpose rather then creating one just for
> arm64 platforms.
> 
> This introduces a new memblock flag MEMBLOCK_BOOT along with helpers which
> can be marked by given platform on all memory regions discovered during
> boot.
 
We already have MEMBLOCK_HOTPLUG to mark hotpluggable region. Can't we use
it for your use-case?

> Cc: Mike Rapoport <rppt@linux.ibm.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> ---
>  include/linux/memblock.h | 10 ++++++++++
>  mm/memblock.c            | 37 +++++++++++++++++++++++++++++++++++++
>  2 files changed, 47 insertions(+)
> 
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index b38bbef..fb04c87 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -31,12 +31,14 @@ extern unsigned long long max_possible_pfn;
>   * @MEMBLOCK_HOTPLUG: hotpluggable region
>   * @MEMBLOCK_MIRROR: mirrored region
>   * @MEMBLOCK_NOMAP: don't add to kernel direct mapping
> + * @MEMBLOCK_BOOT: memory received from firmware during boot
>   */
>  enum memblock_flags {
>  	MEMBLOCK_NONE		= 0x0,	/* No special request */
>  	MEMBLOCK_HOTPLUG	= 0x1,	/* hotpluggable region */
>  	MEMBLOCK_MIRROR		= 0x2,	/* mirrored region */
>  	MEMBLOCK_NOMAP		= 0x4,	/* don't add to kernel direct mapping */
> +	MEMBLOCK_BOOT		= 0x8,	/* memory received from firmware during boot */
>  };
>  
>  /**
> @@ -116,6 +118,8 @@ int memblock_reserve(phys_addr_t base, phys_addr_t size);
>  void memblock_trim_memory(phys_addr_t align);
>  bool memblock_overlaps_region(struct memblock_type *type,
>  			      phys_addr_t base, phys_addr_t size);
> +int memblock_mark_boot(phys_addr_t base, phys_addr_t size);
> +int memblock_clear_boot(phys_addr_t base, phys_addr_t size);
>  int memblock_mark_hotplug(phys_addr_t base, phys_addr_t size);
>  int memblock_clear_hotplug(phys_addr_t base, phys_addr_t size);
>  int memblock_mark_mirror(phys_addr_t base, phys_addr_t size);
> @@ -216,6 +220,11 @@ static inline bool memblock_is_nomap(struct memblock_region *m)
>  	return m->flags & MEMBLOCK_NOMAP;
>  }
>  
> +static inline bool memblock_is_boot(struct memblock_region *m)
> +{
> +	return m->flags & MEMBLOCK_BOOT;
> +}
> +
>  #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
>  int memblock_search_pfn_nid(unsigned long pfn, unsigned long *start_pfn,
>  			    unsigned long  *end_pfn);
> @@ -449,6 +458,7 @@ void memblock_cap_memory_range(phys_addr_t base, phys_addr_t size);
>  void memblock_mem_limit_remove_map(phys_addr_t limit);
>  bool memblock_is_memory(phys_addr_t addr);
>  bool memblock_is_map_memory(phys_addr_t addr);
> +bool memblock_is_boot_memory(phys_addr_t addr);
>  bool memblock_is_region_memory(phys_addr_t base, phys_addr_t size);
>  bool memblock_is_reserved(phys_addr_t addr);
>  bool memblock_is_region_reserved(phys_addr_t base, phys_addr_t size);
> diff --git a/mm/memblock.c b/mm/memblock.c
> index 4bc2c7d..e10207f 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -865,6 +865,30 @@ static int __init_memblock memblock_setclr_flag(phys_addr_t base,
>  }
>  
>  /**
> + * memblock_mark_bootmem - Mark boot memory with flag MEMBLOCK_BOOT.
> + * @base: the base phys addr of the region
> + * @size: the size of the region
> + *
> + * Return: 0 on success, -errno on failure.
> + */
> +int __init_memblock memblock_mark_boot(phys_addr_t base, phys_addr_t size)
> +{
> +	return memblock_setclr_flag(base, size, 1, MEMBLOCK_BOOT);
> +}
> +
> +/**
> + * memblock_clear_bootmem - Clear flag MEMBLOCK_BOOT for a specified region.
> + * @base: the base phys addr of the region
> + * @size: the size of the region
> + *
> + * Return: 0 on success, -errno on failure.
> + */
> +int __init_memblock memblock_clear_boot(phys_addr_t base, phys_addr_t size)
> +{
> +	return memblock_setclr_flag(base, size, 0, MEMBLOCK_BOOT);
> +}
> +
> +/**
>   * memblock_mark_hotplug - Mark hotpluggable memory with flag MEMBLOCK_HOTPLUG.
>   * @base: the base phys addr of the region
>   * @size: the size of the region
> @@ -974,6 +998,10 @@ static bool should_skip_region(struct memblock_region *m, int nid, int flags)
>  	if ((flags & MEMBLOCK_MIRROR) && !memblock_is_mirror(m))
>  		return true;
>  
> +	/* if we want boot memory skip non-boot memory regions */
> +	if ((flags & MEMBLOCK_BOOT) && !memblock_is_boot(m))
> +		return true;
> +
>  	/* skip nomap memory unless we were asked for it explicitly */
>  	if (!(flags & MEMBLOCK_NOMAP) && memblock_is_nomap(m))
>  		return true;
> @@ -1785,6 +1813,15 @@ bool __init_memblock memblock_is_map_memory(phys_addr_t addr)
>  	return !memblock_is_nomap(&memblock.memory.regions[i]);
>  }
>  
> +bool __init_memblock memblock_is_boot_memory(phys_addr_t addr)
> +{
> +	int i = memblock_search(&memblock.memory, addr);
> +
> +	if (i == -1)
> +		return false;
> +	return memblock_is_boot(&memblock.memory.regions[i]);
> +}
> +
>  #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
>  int __init_memblock memblock_search_pfn_nid(unsigned long pfn,
>  			 unsigned long *start_pfn, unsigned long *end_pfn)
> -- 
> 2.7.4
> 

-- 
Sincerely yours,
Mike.