Re: [PATCH v2] bootconfig: Apply early options from embedded config

[Breno Leitao <leitao@debian.org>]

On Fri, Mar 27, 2026 at 10:37:44PM +0900, Masami Hiramatsu wrote:
> On Fri, 27 Mar 2026 03:06:41 -0700
> Breno Leitao <leitao@debian.org> wrote:

> > > To fix this, we need to change setup_arch() for each architecture so
> > > that it calls this bootconfig_apply_early_params().
> > 
> > Could we instead integrate this into parse_early_param() itself? That
> > approach would avoid the need to modify each architecture individually.
> 
> Ah, indeed. 

I investigated integrating bootconfig into parse_early_param() and hit a
blocker: xbc_init() and xbc_make_cmdline() depend on memblock_alloc(), but on
most architectures (x86, arm64, arm, s390, riscv) parse_early_param() is called
from setup_arch() _before_ memblock is initialized.

So, bootconfig will not be available as early as parse_early_param(). 

An alternative is replace memblock allocations in lib/bootconfig.c with static
__initdata buffers, similar to Petr's approach in 2023:

	https://lore.kernel.org/all/20231121231342.193646-3-oss@malat.biz/

But, there was concerns about the allocation size:

	Petr Malat <oss@malat.biz> wrote: 
	> To allow handling of early options, it's necessary to eliminate allocations
	> from embedded bootconfig handling

	"Hm, my concern is that this can introduce some sort of overhead to parse the bootconfig."