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Message-ID: <ZnTRbptoowL+1GOP@ghost>
Date: Thu, 20 Jun 2024 18:03:42 -0700
From: Charlie Jenkins <charlie@...osinc.com>
To: Yunhui Cui <cuiyunhui@...edance.com>
Cc: paul.walmsley@...ive.com, palmer@...belt.com, aou@...s.berkeley.edu,
alexghiti@...osinc.com, akpm@...ux-foundation.org, bhe@...hat.com,
rppt@...nel.org, dawei.li@...ngroup.cn, jszhang@...nel.org,
namcao@...utronix.de, chenjiahao16@...wei.com, bjorn@...osinc.com,
vishal.moola@...il.com, linux-riscv@...ts.infradead.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] RISC-V: cmdline: Add support for 'memmap' parameter
On Tue, Jun 18, 2024 at 08:08:42PM +0800, Yunhui Cui wrote:
> Implement support for parsing 'memmap' kernel command line parameter.
>
> This patch covers parsing of the following two formats for 'memmap'
> parameter values:
>
> - nn[KMG]@ss[KMG]
> - nn[KMG]$ss[KMG]
>
> ([KMG] = K M or G (kilo, mega, giga))
>
> These two allowed formats for parameter value are already documented
> in file kernel-parameters.txt in Documentation/admin-guide folder.
> Some architectures already support them, but Mips did not prior to
Copy-paste from a Mips patch? Should say riscv :)
It looks like this code is duplicated from xtensa and is effectively the
same as mips. Can this code be placed in a generic file so that the code
can be shared between mips, riscv, and xtensa -- maybe a new config that
gets selected by mips/riscv/xtensa?
- Charlie
> this patch.
>
> Excerpt from Documentation/admin-guide/kernel-parameters.txt:
>
> memmap=nn[KMG]@ss[KMG]
> [KNL] Force usage of a specific region of memory.
> Region of memory to be used is from ss to ss+nn.
>
> memmap=nn[KMG]$ss[KMG]
> Mark specific memory as reserved.
> Region of memory to be reserved is from ss to ss+nn.
> Example: Exclude memory from 0x18690000-0x1869ffff
> memmap=64K$0x18690000
> or
> memmap=0x10000$0x18690000
>
> There is no need to update this documentation file with respect to
> this patch.
>
> Signed-off-by: Yunhui Cui <cuiyunhui@...edance.com>
> ---
> arch/riscv/mm/init.c | 50 ++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 50 insertions(+)
>
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index e3405e4b99af..7be7ec3092ad 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -208,6 +208,56 @@ static int __init early_mem(char *p)
> }
> early_param("mem", early_mem);
>
> +static void __init parse_memmap_one(char *p)
> +{
> + char *oldp;
> + unsigned long start_at, mem_size;
> +
> + if (!p)
> + return;
> +
> + oldp = p;
> + mem_size = memparse(p, &p);
> + if (p == oldp)
> + return;
> +
> + switch (*p) {
> + case '@':
> + start_at = memparse(p + 1, &p);
> + memblock_add(start_at, mem_size);
> + break;
> +
> + case '$':
> + start_at = memparse(p + 1, &p);
> + memblock_reserve(start_at, mem_size);
> + break;
> +
> + case 0:
> + memblock_reserve(mem_size, -mem_size);
> + break;
> +
> + default:
> + pr_warn("Unrecognized memmap syntax: %s\n", p);
> + break;
> + }
> +}
> +
> +static int __init parse_memmap_opt(char *str)
> +{
> + while (str) {
> + char *k = strchr(str, ',');
> +
> + if (k)
> + *k++ = 0;
> +
> + parse_memmap_one(str);
> + str = k;
> + }
> +
> + return 0;
> +}
> +early_param("memmap", parse_memmap_opt);
> +
> static void __init setup_bootmem(void)
> {
> phys_addr_t vmlinux_end = __pa_symbol(&_end);
> --
> 2.20.1
>
>
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