[External] Re: [PATCH] RISC-V: cmdline: Add support for 'memmap' parameter

[yunhui cui]

Hi Charlie,

On Fri, Jun 21, 2024 at 9:03 AM Charlie Jenkins <charlie at rivosinc.com> wrote:
>
> 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?

Yeah, that's actually what I was thinking. Which general file do you
think would be more suitable to put it in?

> - 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$0x18690000
> >
> > There is no need to update this documentation file with respect to
> > this patch.
> >
> > Signed-off-by: Yunhui Cui <cuiyunhui at bytedance.com>
> > ---
> >  arch/riscv/mm/init.c | 50 ++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 50 insertions(+)
> >
> > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> > index e3405e4b99af..7be7ec3092ad 100644
> > --- a/arch/riscv/mm/init.c
> > +++ b/arch/riscv/mm/init.c
> > @@ -208,6 +208,56 @@ static int __init early_mem(char *p)
> >  }
> >  early_param("mem", early_mem);
> >
> > +static void __init parse_memmap_one(char *p)
> > +{
> > +     char *oldp;
> > +     unsigned long start_at, mem_size;
> > +
> > +     if (!p)
> > +             return;
> > +
> > +     oldp = p;
> > +     mem_size = memparse(p, &p);
> > +     if (p == oldp)
> > +             return;
> > +
> > +     switch (*p) {
> > +     case '@':
> > +             start_at = memparse(p + 1, &p);
> > +             memblock_add(start_at, mem_size);
> > +             break;
> > +
> > +     case '$':
> > +             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
> >
> >
> > _______________________________________________
> > linux-riscv mailing list
> > linux-riscv at lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-riscv

Thanks,
Yunhui