linux-kernel - Re: [PATCH 15/15] riscv: disable the EFI PECOFF header for M-mode

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Message-ID: <20190821071204.GA25836@lst.de>
Date:   Wed, 21 Aug 2019 09:12:04 +0200
From:   Christoph Hellwig <hch@....de>
To:     Troy Benjegerdes <troy.benjegerdes@...ive.com>
Cc:     Christoph Hellwig <hch@....de>, Palmer Dabbelt <palmer@...ive.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Damien Le Moal <damien.lemoal@....com>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 15/15] riscv: disable the EFI PECOFF header for M-mode

On Tue, Aug 20, 2019 at 09:14:41PM -0700, Troy Benjegerdes wrote:
> 
> 
> > On Aug 13, 2019, at 8:47 AM, Christoph Hellwig <hch@....de> wrote:
> > 
> > No point in bloating the kernel image with a bootloader header if
> > we run bare metal.
> 
> I would say the same for S-mode. EFI booting should be an option, not
> a requirement. I have M-mode U-boot working with bootelf to start BBL,
> and at some point, I’m hoping we can have a M-mode linux kernel be
> the SBI provider for S-mode kernels, which seem most logical to me
> to start using the vmlinux elf binaries using something like kexec()

Strictly speaking we could just add another option for the header so
that you could also disable it for S-mode.  But then again the header
is not very harmful, as you don't have to use it.  It just eats up
a little more kernel space.  And as that aspace is very tight for my
M-mode target (the Kendryte KD210) and it is totally pointless for
M-mode I just remove it there.

The idea of using M-mode Linux as the SBI sounds cool.