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From:   Vineet Gupta <vineet.gupta1@synopsys.com>
To:     Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>,
        "linux-snps-arc@lists.infradead.org" 
        <linux-snps-arc@lists.infradead.org>
CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Alexey Brodkin" <alexey.brodkin@synopsys.com>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: Re: [PATCH] ARC: adjust memblock_reserve of kernel memory
Thread-Topic: [PATCH] ARC: adjust memblock_reserve of kernel memory
Thread-Index: AQHUl7Y3xyclRc6qjkizV/X3iTxkVw==
Date:   Thu, 20 Dec 2018 04:00:39 +0000
Message-ID: <C2D7FE5348E1B147BCA15975FBA23075014642269A@US01WEMBX2.internal.synopsys.com>
References: <20181219161616.10422-1-Eugeniy.Paltsev@synopsys.com>
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On 12/19/18 8:16 AM, Eugeniy Paltsev wrote:=0A=
> In setup_arch_memory we reserve the memory area wherein the kernel=0A=
> is located. Current implementation may reserve more memory than=0A=
> it actually required in case of CONFIG_LINUX_LINK_BASE is not=0A=
> equal to CONFIG_LINUX_RAM_BASE. This happens because we calculate=0A=
> start of the reserved region relatively to the CONFIG_LINUX_RAM_BASE=0A=
> and end of the region relatively to the CONFIG_LINUX_RAM_BASE.=0A=
>=0A=
> For example in case of HSDK board we wasted 256MiB of physical memory:=0A=
> ------------------->8------------------------------=0A=
> Memory: 770416K/1048576K available (5496K kernel code,=0A=
>     240K rwdata, 1064K rodata, 2200K init, 275K bss,=0A=
>     278160K reserved, 0K cma-reserved)=0A=
> ------------------->8------------------------------=0A=
>=0A=
> Fix that.=0A=
>=0A=
> Cc: stable@vger.kernel.org=0A=
=0A=
For backports, please also check how far back this needs to be applied (els=
e we=0A=
get bot emails specifying they don't apply to ver x, y z)=0A=
=0A=
> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>=0A=
> ---=0A=
>  arch/arc/mm/init.c | 3 ++-=0A=
>  1 file changed, 2 insertions(+), 1 deletion(-)=0A=
>=0A=
> diff --git a/arch/arc/mm/init.c b/arch/arc/mm/init.c=0A=
> index f8fe5668b30f..a56e6a8ed259 100644=0A=
> --- a/arch/arc/mm/init.c=0A=
> +++ b/arch/arc/mm/init.c=0A=
> @@ -137,7 +137,8 @@ void __init setup_arch_memory(void)=0A=
>  	 */=0A=
>  =0A=
>  	memblock_add_node(low_mem_start, low_mem_sz, 0);=0A=
> -	memblock_reserve(low_mem_start, __pa(_end) - low_mem_start);=0A=
> +	memblock_reserve(CONFIG_LINUX_LINK_BASE,=0A=
> +			 __pa(_end) - CONFIG_LINUX_LINK_BASE);=0A=
>  =0A=
>  #ifdef CONFIG_BLK_DEV_INITRD=0A=
>  	if (initrd_start)=0A=
=0A=
So I looked into the history for restricting stable, and it seems this was=
=0A=
introduced with our earlier work for HSDK.=0A=
=0A=
Before commit 9ed68785f7f this code was ok, since low_mem_start =3D=0A=
CONFIG_LINUX_LINK_BASE.=0A=
With the patch we changed low_mem_start to CONFIG_LINUX_RAM_BASE and missed=
 this.=0A=
=0A=
-Vineet=0A=