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        Jessica Clarke <jrtc27@jrtc27.com>,
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        weidong.wd@bytedance.com
Subject: Re: [External] [PATCH v2 1/3] riscv: obtain ACPI RSDP from FFI.
In-Reply-To: <50F3BD62-78F1-456E-A44A-0C7D9A2D4113@jrtc27.com>
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Date:   Wed, 05 Jul 2023 16:42:33 +0200
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Jessica Clarke <jrtc27@jrtc27.com> writes:

> On 3 Jul 2023, at 19:58, Emil Renner Berthing <emil.renner.berthing@gmail=
.com> wrote:
>>=20
>> On Mon, 3 Jul 2023 at 15:33, =E8=BF=90=E8=BE=89=E5=B4=94 <cuiyunhui@byte=
dance.com> wrote:
>>>=20
>>> Hi drew,
>>>=20
>>> On Mon, Jul 3, 2023 at 9:01=E2=80=AFPM Andrew Jones <ajones@ventanamicr=
o.com> wrote:
>>>>=20
>>>>=20
>>>> (This is a reply to a non-existent cover letter.)
>>>=20
>>> This has been discussed many times with Ard, Please refer to :
>>> https://patches.linaro.org/project/linux-acpi/patch/20230426034001.16-1=
-cuiyunhui@bytedance.com/
>>=20
>> Hi Yunhui,
>>=20
>> From that discussion it was mentioned that that arm supports 3 methods
>> of booting:
>>  direct + devicetree
>>  EFI + devicetree
>>  EFI + ACPI
>> ..but not
>>  direct + ACPI
>>=20
>> To me it isn't obvious from that or this thread, and since arm seems
>> to be doing fine without the 4th option I'm curious why that's
>> necessary on riscv?
>
> If anything we should be removing option 1, because that=E2=80=99s not a
> cross-OS standard (though RISC-V=E2=80=99s SBI direct booting is at least=
 not
> tied to the OS). Any application-class platform spec is going to
> mandate EFI, because, whatever your thoughts of EFI are, that is *the*
> standard. And if you=E2=80=99re willing to pick up all the complexity of =
ACPI,
> what=E2=80=99s a bit of EFI (especially if you only go for a minimal one =
a la
> U-Boot)?

Well said!

Yunhui, why not simply add a minimal UEFI stub to Coreboot (like Jess
points out above)?

IMO what U-boot (or
https://github.com/cloud-hypervisor/rust-hypervisor-firmware if you're
into Rust ;-)) is doing, and just having a small UEFI shim is the way to
go.