On 2021/12/29 18:46, Dave Young wrote:

On 12/29/21 at 11:03am, Borislav Petkov wrote:

quoted

On Wed, Dec 29, 2021 at 03:27:48PM +0800, Dave Young wrote:

quoted

So I think you can unify the parse_crashkernel* in x86 first with just
one function.  And leave the further improvements to later work. But
let's see how Boris think about this.

Well, I think this all unnecessary work. Why?

If the goal is to support crashkernel...high,low on arm64, then you
should simply *copy* the functionality on arm64 and be done with it.

Unification is done by looking at code which is duplicated across
architectures and which has been untouched for a while now, i.e., no
new or arch-specific changes are going to it so a unification can be
as simple as trivially switching the architectures to call a generic
function.

What this does is carve out the "generic" parts and then try not to
break existing usage.

Which is a total waste of energy and resources. And it is casting that
functionality in stone so that when x86 wants to change something there,
it should do it in a way not to break arm64. And I fail to see the
advantage of all that. Code sharing ain't it.

It's just a worry, there's uncertainty about whether it's going to be. I think
the only thing that might change is the default value of "low_size". Of course,
the alignment size and start address may also change, but most of them can be
controlled by macros.

Chen Zhou and I tried to share the code because of a suggestion. After so many
attempts, it doesn't seem to fit to make generic. Or maybe I haven't figured
out a good solution yet.

quoted

So what it should do is simply copy the necessary code to arm64.
Unifications can always be done later, when the dust settles.

I think I agree with you about the better way is to doing some
improvements so that arches can logically doing things better.  I can
leave with the way I suggested although it is not the best.  But I think
Leizhen needs a clear direction about how to do it. It is very clear
now.  See how he will handle this. 

Surviving, then pursuing ideals.

I will put the patches that make arm64 support crashkernel...high,low to
the front, then the parse_crashkernel() unification patches. Even if the
second half of the patches is not ready for v5.18, the first half of the
patches is ready.

quoted

IMNSVHO.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

.

-- 
Regards,
  Zhen Lei

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