linux-kernel - Re: [PATCH v3 2/6] arm64/mirror: arm64 enabling

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Date:   Fri, 10 Jun 2022 11:34:46 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Kefeng Wang <wangkefeng.wang@...wei.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>,
        Kees Cook <keescook@...omium.org>, songmuchun@...edance.com,
        Randy Dunlap <rdunlap@...radead.org>,
        damien.lemoal@...nsource.wdc.com,
        Stephen Boyd <swboyd@...omium.org>,
        Wei Liu <wei.liu@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        David Hildenbrand <david@...hat.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Zhen Lei <thunder.leizhen@...wei.com>, gpiccoli@...lia.com,
        Huacai Chen <chenhuacai@...nel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        vijayb@...ux.microsoft.com,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-efi <linux-efi@...r.kernel.org>,
        platform-driver-x86@...r.kernel.org,
        Linux Memory Management List <linux-mm@...ck.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH v3 2/6] arm64/mirror: arm64 enabling - find mirrored
 memory ranges

On Fri, 10 Jun 2022 at 11:27, Kefeng Wang <wangkefeng.wang@...wei.com> wrote:
>
>
> On 2022/6/7 17:38, Wupeng Ma wrote:
> > From: Ma Wupeng <mawupeng1@...wei.com>
> >
> > Commit b05b9f5f9dcf ("x86, mirror: x86 enabling - find mirrored memory ranges")
> > introduced mirrored memory support for x86 and this could be used on arm64.
> >
> > Since we only support this feature on arm64, efi_find_mirror() won't be placed
> > into efi_init(), which is used by riscv/arm/arm64, it is added in setup_arch()
> > to scan the memory map and mark mirrored memory in memblock.
>
> Move into efi_init() looks better, it won't bring negative effects on
> arm/riscv.
>
> but let's maintainer to make a decision.
>
> Reviewed-by: Kefeng Wang <wangkefeng.wang@...wei.com>
>

I don't disagree with that in principle, but x86 calls the efi fake
memmap stuff between efi_init() and efi_find_mirror(), and I already
indicated that I don't want to enable fake memmap on !X86.

But I do think there is some room for improvement here: we could move
things like efi_mokvar_table_init() and efi_esrt_init() into
efi_init() as well, and make efi_fake_memmap() do nothing on !X86 so
we can move it into efi_init() too.

> >
> > Signed-off-by: Ma Wupeng <mawupeng1@...wei.com>
> > ---
> >   Documentation/admin-guide/kernel-parameters.txt | 2 +-
> >   arch/arm64/kernel/setup.c                       | 1 +
> >   2 files changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> > index 8090130b544b..e3537646b6f7 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -2301,7 +2301,7 @@
> >
> >       keepinitrd      [HW,ARM]
> >
> > -     kernelcore=     [KNL,X86,IA-64,PPC]
> > +     kernelcore=     [KNL,X86,IA-64,PPC,ARM64]
> >                       Format: nn[KMGTPE] | nn% | "mirror"
> >                       This parameter specifies the amount of memory usable by
> >                       the kernel for non-movable allocations.  The requested
> > diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> > index cf3a759f10d4..6e9acd7ecf0f 100644
> > --- a/arch/arm64/kernel/setup.c
> > +++ b/arch/arm64/kernel/setup.c
> > @@ -328,6 +328,7 @@ void __init __no_sanitize_address setup_arch(char **cmdline_p)
> >
> >       xen_early_init();
> >       efi_init();
> > +     efi_find_mirror();
> >
> >       if (!efi_enabled(EFI_BOOT) && ((u64)_text % MIN_KIMG_ALIGN) != 0)
> >            pr_warn(FW_BUG "Kernel image misaligned at boot, please fix your bootloader!");