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Date:   Thu, 8 Nov 2018 18:18:23 +0200
From:   Mike Rapoport <rppt@linux.ibm.com>
To:     Thomas Bogendoerfer <tbogendoerfer@suse.de>
Cc:     Ralf Baechle <ralf@linux-mips.org>,
        Paul Burton <paul.burton@mips.com>,
        James Hogan <jhogan@kernel.org>,
        Huacai Chen <chenhc@lemote.com>, linux-mips@linux-mips.org,
        linux-kernel@vger.kernel.org, rppt@linux.vnet.ibm.com
Subject: Re: [[PATCH]] mips: Fix switch to NO_BOOTMEM for SGI-IP27/loongons3
 NUMA
References: <20181108144428.28149-1-tbogendoerfer@suse.de>
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On Thu, Nov 08, 2018 at 03:44:28PM +0100, Thomas Bogendoerfer wrote:
> Commit bcec54bf3118 ("mips: switch to NO_BOOTMEM") broke SGI-IP27
> and NUMA enabled loongson3 by doing memblock_set_current_limit()
> before max_low_pfn has been evaluated. Both platforms need to do the
> memblock_set_current_limit() in platform specific code. For
> consistency the call to memblock_set_current_limit() is moved
> to the common bootmem_init(), where max_low_pfn is calculated
> for non NUMA enabled platforms.

As far as I can tell loongsoon3 initially sets max_low_pfn in
node_mem_init(0) and then re-evaluates it in paging_init(). So it seems
that in this case the limit would be wrong for a system with more than one
node, but it would be set to some usable value.

As for SGI-IP27, the initialization of max_low_pfn as late as in
paging_init() seems to be broken because it's value is used in
arch_mem_init() and in finalize_initrd() anyway.

AFAIU, both platforms set max_low_pfn to last available pfn, so it seems we
can simply do

	max_low_pfn = PFN_PHYS(memblock_end_of_DRAM())

in the prom_meminit() function for both platforms and drop the loop
evaluating max_low_pfn in paging_init().
 
> Fixes: bcec54bf3118 ("mips: switch to NO_BOOTMEM")
> Signed-off-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
> ---
>  arch/mips/kernel/setup.c               | 18 +++++++++---------
>  arch/mips/loongson64/loongson-3/numa.c |  1 +
>  arch/mips/sgi-ip27/ip27-memory.c       |  1 +
>  3 files changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
> index ea09ed6a80a9..b5167b198231 100644
> --- a/arch/mips/kernel/setup.c
> +++ b/arch/mips/kernel/setup.c
> @@ -576,6 +576,15 @@ static void __init bootmem_init(void)
>  	 * Reserve initrd memory if needed.
>  	 */
>  	finalize_initrd();
> +
> +	/*
> +	 * Prevent memblock from allocating high memory.
> +	 * This cannot be done before max_low_pfn is detected, so up
> +	 * to this point is possible to only reserve physical memory
> +	 * with memblock_reserve; memblock_alloc* can be used
> +	 * only after this point
> +	 */
> +	memblock_set_current_limit(PFN_PHYS(max_low_pfn));
>  }
> 
>  #endif	/* CONFIG_SGI_IP27 */
> @@ -854,15 +863,6 @@ static void __init arch_mem_init(char **cmdline_p)
> 
>  	bootmem_init();
> 
> -	/*
> -	 * Prevent memblock from allocating high memory.
> -	 * This cannot be done before max_low_pfn is detected, so up
> -	 * to this point is possible to only reserve physical memory
> -	 * with memblock_reserve; memblock_alloc* can be used
> -	 * only after this point
> -	 */
> -	memblock_set_current_limit(PFN_PHYS(max_low_pfn));
> -
>  #ifdef CONFIG_PROC_VMCORE
>  	if (setup_elfcorehdr && setup_elfcorehdr_size) {
>  		printk(KERN_INFO "kdump reserved memory at %lx-%lx\n",
> diff --git a/arch/mips/loongson64/loongson-3/numa.c b/arch/mips/loongson64/loongson-3/numa.c
> index 622761878cd1..5593a8e3cd88 100644
> --- a/arch/mips/loongson64/loongson-3/numa.c
> +++ b/arch/mips/loongson64/loongson-3/numa.c
> @@ -265,6 +265,7 @@ void __init paging_init(void)
>  	zones_size[ZONE_DMA32] = MAX_DMA32_PFN;
>  #endif
>  	zones_size[ZONE_NORMAL] = max_low_pfn;
> +	memblock_set_current_limit(PFN_PHYS(max_low_pfn));
>  	free_area_init_nodes(zones_size);
>  }
> 
> diff --git a/arch/mips/sgi-ip27/ip27-memory.c b/arch/mips/sgi-ip27/ip27-memory.c
> index d8b8444d6795..0d0deeae1f47 100644
> --- a/arch/mips/sgi-ip27/ip27-memory.c
> +++ b/arch/mips/sgi-ip27/ip27-memory.c
> @@ -468,6 +468,7 @@ void __init paging_init(void)
>  			max_low_pfn = end_pfn;
>  	}
>  	zones_size[ZONE_NORMAL] = max_low_pfn;
> +	memblock_set_current_limit(PFN_PHYS(max_low_pfn));
>  	free_area_init_nodes(zones_size);
>  }
> 
> -- 
> 2.13.7
> 

-- 
Sincerely yours,
Mike.