linux-kernel - Re: [PATCH] x86/boot/e820: add new chareater "-" to free BIOS memory in memmap bootargs

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Date:   Mon, 16 Apr 2018 19:06:37 +0800
From:   zoucao-ipc <zoucaox@...il.com>
To:     zoucao@...ux.alibaba.com, tglx@...utronix.de, mingo@...hat.com,
        hpa@...or.com
CC:     x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/boot/e820: add new chareater "-" to free BIOS memory
 in memmap bootargs

any suggestions？

On 2018/4/10 上午10:59, zoucao@...ux.alibaba.com wrote:
> From: zoucao <zoucao@...alhost.localdomain>
>
> Normally every BIOS reserved memory is used for some features, we can't
> use them, but in some conditions,  users can ensure some BIOS memories
> are not used and reserved memory is well to free, they have not a good
> way to free these memories, here add a new chareater "-" in memmap to
> free reserved memory.
>
> Signed-off-by: zou cao <zoucao@...ux.alibaba.com>
> ---
>   7u/Documentation/kernel-parameters.txt | 6 ++++++
>   7u/arch/x86/kernel/e820.c              | 3 +++
>   2 files changed, 9 insertions(+)
>
> diff --git a/7u/Documentation/kernel-parameters.txt b/7u/Documentation/kernel-parameters.txt
> index 9a1abb99a..dbea75e12 100644
> --- a/7u/Documentation/kernel-parameters.txt
> +++ b/7u/Documentation/kernel-parameters.txt
> @@ -1677,6 +1677,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
>   			         or
>   			         memmap=0x10000$0x18690000
>   
> +	memmap=nn[KMG]-ss[KMG]
> +			Free E820 reserved memory, as specified by the user.
> +			Region of reserved memory to be free, from ss to ss+nn.
> +			Example: free reserved memory from 0x18690000-0x186a0000
> +					memmap=0x4101000-0x6aeff000
> +
>   	memory_corruption_check=0/1 [X86]
>   			Some BIOSes seem to corrupt the first 64k of
>   			memory when doing things like suspend/resume.
> diff --git a/7u/arch/x86/kernel/e820.c b/7u/arch/x86/kernel/e820.c
> index 174da5fc5..b8a042981 100644
> --- a/7u/arch/x86/kernel/e820.c
> +++ b/7u/arch/x86/kernel/e820.c
> @@ -875,6 +875,9 @@ static int __init parse_memmap_one(char *p)
>   	} else if (*p == '$') {
>   		start_at = memparse(p+1, &p);
>   		e820_add_region(start_at, mem_size, E820_RESERVED);
> +	} else if (*p == '-') {
> +		start_at = memparse(p+1, &p);
> +		e820_remove_range(start_at, mem_size, E820_RESERVED, E820_RAM);
>   	} else
>   		e820_remove_range(mem_size, ULLONG_MAX - mem_size, E820_RAM, 1);
>