linux-kernel - Re: [PATCH] arm: skip nomap memblocks while finding the lowmem/highmem boundary

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Date:   Thu, 22 Aug 2019 03:59:42 +0000
From:   Chester Lin <clin@...e.com>
To:     "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "rppt@...ux.ibm.com" <rppt@...ux.ibm.com>,
        "ard.biesheuvel@...aro.org" <ard.biesheuvel@...aro.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "geert@...ux-m68k.org" <geert@...ux-m68k.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mark.rutland@....com" <mark.rutland@....com>
CC:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "guillaume.gardet@....com" <guillaume.gardet@....com>,
        Gary Lin <GLin@...e.com>, Joey Lee <JLee@...e.com>
Subject: Re: [PATCH] arm: skip nomap memblocks while finding the
 lowmem/highmem boundary

On Thu, Aug 22, 2019 at 11:45:34AM +0800, Chester Lin wrote:
> adjust_lowmem_bounds() checks every memblocks in order to find the boundary
> between lowmem and highmem. However some memblocks could be marked as NOMAP
> so they are not used by kernel, which should be skipped while calculating
> the boundary.
> 
> Signed-off-by: Chester Lin <clin@...e.com>
> ---
>  arch/arm/mm/mmu.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> index 426d9085396b..b86dba44d828 100644
> --- a/arch/arm/mm/mmu.c
> +++ b/arch/arm/mm/mmu.c
> @@ -1181,6 +1181,9 @@ void __init adjust_lowmem_bounds(void)
>  		phys_addr_t block_start = reg->base;
>  		phys_addr_t block_end = reg->base + reg->size;
>  
> +		if (memblock_is_nomap(reg))
> +			continue;
> +
>  		if (reg->base < vmalloc_limit) {
>  			if (block_end > lowmem_limit)
>  				/*
> -- 
> 2.22.0
>

Hi Russell, Mike and Ard,

Per the discussion in the thread "[PATH] efi/arm: fix allocation failure ...",
(https://lkml.org/lkml/2019/8/21/163), I presume that the change to disregard
NOMAP memblocks in adjust_lowmem_bounds() should be separated as a single patch.

Please let me know if any suggestion, thank you.