Re: [PATCH] arm64/mm: Delete __init region from memblock.reserved

[Rong Qianfeng]

在 2024/8/30 16:14, Ard Biesheuvel 写道:
> Hi Rong,
>
> On Fri, 30 Aug 2024 at 10:00, Rong Qianfeng <rongqianfeng@xxxxxxxx> wrote:
> > If CONFIG_ARCH_KEEP_MEMBLOCK is enabled, the memory information in
> > memblock will be retained. We release the __init memory here, and
> > we should also delete the corresponding region in memblock.reserved.
> >
> > Signed-off-by: Rong Qianfeng <rongqianfeng@xxxxxxxx>
> > ---
> >   arch/arm64/mm/init.c | 7 +++++++
> >   1 file changed, 7 insertions(+)
> >
> > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> > index bfb10969cbf0..99cfa217e905 100644
> > --- a/arch/arm64/mm/init.c
> > +++ b/arch/arm64/mm/init.c
> > @@ -402,6 +402,13 @@ void __init mem_init(void)
> >
> >   void free_initmem(void)
> >   {
> > +       if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) {
> This is always true on arm64
>
> > +               unsigned long aligned_begin = ALIGN_DOWN((u64)__init_begin, PAGE_SIZE);
> > +               unsigned long aligned_end = ALIGN((u64)__init_end, PAGE_SIZE);
> > +
> > +               memblock_free((void *)aligned_begin, aligned_end - aligned_begin);
> > +       }
> > +
> What does this achieve? The memory is already being reused by the page
> allocator (due to free_reserved_area()), and the memblock allocator is
> no longer usable at this point anyway.
If not,  incorrect information will be visible in
/sys/kernel/debug/memblock/reserved.

Best Regards,
Qianfeng
> >          free_reserved_area(lm_alias(__init_begin),
> >                             lm_alias(__init_end),
> >                             POISON_FREE_INITMEM, "unused kernel");