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Message-ID: <CAMj1kXGXvjrnY=Hzd4c3CYZsNT6OiqTcMmKT0tdnk=jFOiVpWA@mail.gmail.com>
Date: Tue, 14 Jun 2022 12:27:15 +0200
From: Ard Biesheuvel <ardb@...nel.org>
To: Baoquan He <bhe@...hat.com>
Cc: Wupeng Ma <mawupeng1@...wei.com>, Jonathan Corbet <corbet@....net>,
Will Deacon <will@...nel.org>,
Catalin Marinas <catalin.marinas@....com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
X86 ML <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
Darren Hart <dvhart@...radead.org>,
Andy Shevchenko <andy@...radead.org>,
Mike Rapoport <rppt@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
"Paul E. McKenney" <paulmck@...nel.org>,
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Randy Dunlap <rdunlap@...radead.org>,
damien.lemoal@...nsource.wdc.com,
Stephen Boyd <swboyd@...omium.org>,
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David Hildenbrand <david@...hat.com>,
Anshuman Khandual <anshuman.khandual@....com>,
Zhen Lei <thunder.leizhen@...wei.com>,
Kefeng Wang <wangkefeng.wang@...wei.com>, gpiccoli@...lia.com,
Huacai Chen <chenhuacai@...nel.org>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
vijayb@...ux.microsoft.com,
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Linux Memory Management List <linux-mm@...ck.org>,
linux-riscv <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH v5 5/5] memblock: Disable mirror feature if kernelcore is
not specified
On Tue, 14 Jun 2022 at 12:20, Baoquan He <bhe@...hat.com> wrote:
>
> On 06/14/22 at 05:21pm, Wupeng Ma wrote:
> > From: Ma Wupeng <mawupeng1@...wei.com>
> >
> > If system have some mirrored memory and mirrored feature is not specified
> > in boot parameter, the basic mirrored feature will be enabled and this will
> > lead to the following situations:
> >
> > - memblock memory allocation prefers mirrored region. This may have some
> > unexpected influence on numa affinity.
> >
> > - contiguous memory will be split into several parts if parts of them
> > is mirrored memory via memblock_mark_mirror().
> >
> > To fix this, variable mirrored_kernelcore will be checked in
> > memblock_mark_mirror(). Mark mirrored memory with flag MEMBLOCK_MIRROR iff
> > kernelcore=mirror is added in the kernel parameters.
> >
> > Signed-off-by: Ma Wupeng <mawupeng1@...wei.com>
> > Acked-by: Ard Biesheuvel <ardb@...nel.org>
> > ---
> > mm/internal.h | 2 ++
> > mm/memblock.c | 3 +++
> > mm/page_alloc.c | 2 +-
> > 3 files changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/internal.h b/mm/internal.h
> > index c0f8fbe0445b..ddd2d6a46f1b 100644
> > --- a/mm/internal.h
> > +++ b/mm/internal.h
> > @@ -861,4 +861,6 @@ struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags);
> >
> > DECLARE_PER_CPU(struct per_cpu_nodestat, boot_nodestats);
> >
> > +extern bool mirrored_kernelcore;
> > +
> > #endif /* __MM_INTERNAL_H */
> > diff --git a/mm/memblock.c b/mm/memblock.c
> > index b1d2a0009733..a9f18b988b7f 100644
> > --- a/mm/memblock.c
> > +++ b/mm/memblock.c
> > @@ -924,6 +924,9 @@ int __init_memblock memblock_clear_hotplug(phys_addr_t base, phys_addr_t size)
> > */
> > int __init_memblock memblock_mark_mirror(phys_addr_t base, phys_addr_t size)
> > {
> > + if (!mirrored_kernelcore)
> > + return 0;
>
> memblock_mark_mirror() is just a wrapper, maybe we should check this in
> efi_find_mirror(). Otherwise, how do we explain the message printed out
> at below in boot log if we don't mark mirror memory at all?
>
> void __init efi_find_mirror(void)
> {
> ......
> if (mirror_size)
> pr_info("Memory: %lldM/%lldM mirrored memory\n",
> mirror_size>>20, total_size>>20);
> }
>
EFI does not care about *how* mirrored memory is being used or not, it
just reports what the firmware provided. So EFI is not the appropriate
level to take kernelcore=mirror into account.
I already mentioned that memblock_mark_mirror() is also the wrong
place IMO, but Kefeng explained that doing it elsewhere is
problematic.
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