linux-kernel - Re: [RFC PATCH 15/27] of/fdt: Introduce early_init_dt_add_memory

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Date:   Tue, 17 Nov 2020 13:44:53 -0600
From:   Rob Herring <robh+dt@...nel.org>
To:     Quentin Perret <qperret@...gle.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Frank Rowand <frowand.list@...il.com>,
        "moderated list:ARM64 PORT (AARCH64 ARCHITECTURE)" 
        <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:KERNEL VIRTUAL MACHINE FOR ARM64 (KVM/arm64)" 
        <kvmarm@...ts.cs.columbia.edu>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE" 
        <devicetree@...r.kernel.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        android-kvm@...gle.com
Subject: Re: [RFC PATCH 15/27] of/fdt: Introduce early_init_dt_add_memory_hyp()

On Tue, Nov 17, 2020 at 12:16 PM Quentin Perret <qperret@...gle.com> wrote:
>
> Introduce early_init_dt_add_memory_hyp() to allow KVM to conserve a copy
> of the memory regions parsed from DT. This will be needed in the context
> of the protected nVHE feature of KVM/arm64 where the code running at EL2
> will be cleanly separated from the host kernel during boot, and will
> need its own representation of memory.
>
> Signed-off-by: Quentin Perret <qperret@...gle.com>
> ---
>  drivers/of/fdt.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index 4602e467ca8b..af2b5a09c5b4 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -1099,6 +1099,10 @@ int __init early_init_dt_scan_chosen(unsigned long node, const char *uname,
>  #define MAX_MEMBLOCK_ADDR      ((phys_addr_t)~0)
>  #endif
>
> +void __init __weak early_init_dt_add_memory_hyp(u64 base, u64 size)
> +{
> +}
> +
>  void __init __weak early_init_dt_add_memory_arch(u64 base, u64 size)
>  {
>         const u64 phys_offset = MIN_MEMBLOCK_ADDR;
> @@ -1139,6 +1143,7 @@ void __init __weak early_init_dt_add_memory_arch(u64 base, u64 size)
>                 base = phys_offset;
>         }
>         memblock_add(base, size);
> +       early_init_dt_add_memory_hyp(base, size);

Can this be done right after we add all the memblocks using the
memblock API? I thought EFI would also need to be handled, but looks
like it just calls early_init_dt_add_memory_arch(). That's odd
especially for ACPI systems...

I don't really like putting what looks like an arm64 only hook here,
but then I don't want an arm64 version of
early_init_dt_add_memory_arch() either. We're almost to the point of
getting rid of the arch specific ones. But I don't have a better
suggestion currently.

Rob