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From:   Huacai Chen <chenhuacai@gmail.com>
Date:   Fri, 6 May 2022 21:20:49 +0800
Message-ID: <CAAhV-H5FbA5DJvPwygiUyBrzq9M5R=Fr06rHAHLR31uu6ZLmkQ@mail.gmail.com>
Subject: Re: [PATCH V9 20/24] LoongArch: Add efistub booting support
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     WANG Xuerui <kernel@xen0n.name>, Ard Biesheuvel <ardb@kernel.org>,
        Huacai Chen <chenhuacai@loongson.cn>,
        Andy Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        David Airlie <airlied@linux.ie>,
        Jonathan Corbet <corbet@lwn.net>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Xuefeng Li <lixuefeng@loongson.cn>,
        Yanteng Si <siyanteng@loongson.cn>,
        Guo Ren <guoren@kernel.org>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>
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Hi, Ard, Arnd and Xuerui,

On Fri, May 6, 2022 at 7:41 PM Arnd Bergmann <arnd@arndb.de> wrote:
>
> On Fri, May 6, 2022 at 1:26 PM WANG Xuerui <kernel@xen0n.name> wrote:
> > On 5/6/22 16:14, Ard Biesheuvel wrote:
>
> > Or is there compatibility at all?
> >
> > It turns out that this port is already incompatible with shipped
> > systems, in other ways, at least since the March revision or so.
>
> I think we can treat user space compatibility separately from firmware
> compatibility.
>
> > So, in effect, this port is starting from scratch, and taking the chance
> > to fix early mistakes and oversights all over; hence my opinion is,
> > better do the Right Thing (tm) and give the generic codepath a chance.
> >
> > For the Loongson devs: at least, declare the struct boot_params flow
> > deprecated from day one, then work to eliminate it from future products,
> > if you really don't want to delay merging even further (it's already
> > unlikely to land in 5.19, given the discussion happening in LKML [3]).
> > It's not embarrassing to admit mistakes; we all make mistakes, and
> > what's important is to learn from them so we don't collectively repeat
> > ourselves.
>
> Agreed. I think there can be limited compatibility support for old
> firmware though, at least to help with the migration: As long as
> the interface between grub and linux has a proper definition following
> the normal UEFI standard, there can be both a modern grub
> that is booted using the same protocol and a backwards-compatible
> grub that can be booted from existing firmware and that is able
> to boot the kernel.
>
> The compatibility version of grub can be retired after the firmware
> itself is able to speak the normal boot protocol.
After an internal discussion, we decide to use the generic stub, and
we have a draft version of generic stub now[1]. I hope V10 can solve
all problems. :)
[1] https://github.com/loongson/linux/tree/loongarch-next-generic-stub

Huacai
>
>        Arnd