Re: [RESEND PATCH v5 07/11] ppc64/kexec_file: enable early kernel's OPAL calls

From: Hari Bathini
Date: Tue Jul 28 2020 - 15:25:11 EST

On 28/07/20 7:16 pm, Michael Ellerman wrote:
Hari Bathini <hbathini@xxxxxxxxxxxxx> writes:
Kernel built with CONFIG_PPC_EARLY_DEBUG_OPAL enabled expects r8 & r9
to be filled with OPAL base & entry addresses respectively. Setting
these registers allows the kernel to perform OPAL calls before the
device tree is parsed.

I'm not convinced we want to do this.

If we do it becomes part of the kexec ABI and we have to honour it into
the future.

And in practice there are no non-development kernels built with OPAL early
debugging enabled, so it's not clear it actually helps anyone other than

Hmmm.. kexec-tools does it since commit d58ad564852c ("kexec/ppc64
Enable early kernel's OPAL calls") for kexec_load syscall. So, we would
be breaking kexec ABI either way, I guess.

Let me put this patch at the end of the series in the respin to let you
decide whether to have it or not..