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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Sun, 1 May 2022 10:33:29 +0200
Message-ID: <CAK8P3a0E7P_TOJsT9=+O56L2=oyeMGckTvkb4OnK1MPcETLdtg@mail.gmail.com>
Subject: Re: [PATCH V9 21/24] LoongArch: Add zboot (compressed kernel) support
To:     Huacai Chen <chenhuacai@gmail.com>
Cc:     Arnd Bergmann <arnd@arndb.de>,
        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>, Xuerui Wang <kernel@xen0n.name>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        linux-riscv <linux-riscv@lists.infradead.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Ard Biesheuvel <ardb@kernel.org>,
        linux-efi <linux-efi@vger.kernel.org>
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On Sun, May 1, 2022 at 7:22 AM Huacai Chen <chenhuacai@gmail.com> wrote:
> On Sat, Apr 30, 2022 at 7:02 PM Arnd Bergmann <arnd@arndb.de> wrote:
> > On Sat, Apr 30, 2022 at 11:05 AM Huacai Chen <chenhuacai@loongson.cn> wrote:
> > >
> > > This patch adds zboot (self-extracting compressed kernel) support, all
> > > existing in-kernel compressing algorithm and efistub are supported.
> > >
> > > Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
> >
> > I have no objections to adding a decompressor in principle, and
> > the implementation seems reasonable. However, I think we should try to
> > be consistent between architectures. On both arm64 and riscv, the
> > maintainers decided to not include a decompressor and instead leave
> > it up to the boot loader to decompress the kernel and enter it from there.
>
> X86, ARM32 and MIPS already support self-extracting kernel, and in
> 5.17 we even support self-extracting modules. So I think a
> self-extracting kernel is better than a pure compressed kernel.

These three support it because they always have and it's hard to
remove features later because it breaks user setups. Among the
architectures we merged since the start of the git history in 2005, only
xtensa supports compressed kernels, the rest rely on the boot loader.

> > Adding the arm64, risc-v and uefi maintainers for further discussion here,
> > see full below.
>
> Keeping consistency across architectures (support self-extracting for
> all modern architectures) looks good to me, but can we do that after
> this series? I think that needs a long time to discuss and develop.

Right, just drop this patch then, and we can get back to doing it for
all UEFI users after loongarch is merged.

      Arnd