Re: [PATCH V9 21/24] LoongArch: Add zboot (compressed kernel) support

From: "Russell King (Oracle)" <linux@armlinux.org.uk>
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>
Subject: Re: [PATCH V9 21/24] LoongArch: Add zboot (compressed kernel) support
Date: Sun, 1 May 2022 07:35:32 +0100	[thread overview]
Message-ID: <Ym4qNILcz+W7dC9i@shell.armlinux.org.uk> (raw)
In-Reply-To: <CAAhV-H6vPdLeup38YTj64Xxxk+PTact=DMJTs9efsa1b3t-y2A@mail.gmail.com>

On Sun, May 01, 2022 at 01:22:25PM +0800, Huacai Chen wrote:
> Hi, Arnd,
> 
> 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.

FYI, kernel modules are not self-extracting. They don't contain the code
to do the decompression - that is contained within the kernel, and it is
the kernel that does the decompression. The userspace tooling tells the
kernel that the module is compressed.

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