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

[Charlie Jenkins]

On Fri, Jun 21, 2024 at 10:08:39AM +0800, yunhui cui wrote:
> 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?

I am not sure the best place to put it. What do you think about
mm/memblock.c next to the "memblock" early param?

> 
> > - 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