Le 04/05/2021 à 14:17, Michal Suchánek a écrit :

On Tue, May 04, 2021 at 02:09:24PM +0200, Miguel Ojeda wrote:

quoted

On Tue, May 4, 2021 at 11:22 AM Michal Suchánek [off-list ref] wrote:

quoted

Except it makes answering the question "Is this bug we see on this
ancient system still present in upstream?" needlessly more difficult to
answer.

Can you please provide some details? If you are talking about testing
a new kernel image in the ancient system "as-is", why wouldn't you
build it in a newer system? If you are talking about  particular
problems about bisecting (kernel, compiler) pairs etc., details would
also be welcome.

Yes, bisecting comes to mind. If you need to switch the userspace as
well the bisection results are not that solid. You may not be even able
to bisect because the workload does not exist on a new system at all.
Crafting a minimal test case that can be forward-ported to a new system
is not always trivial - if you understood the problem to that extent you
might not even need to bisect it in the first place.

But you don't need to switch the userspace or the complete build tools to build a kernel with a 
newer toolchain.

All you have to do is take one from https://mirrors.edge.kernel.org/pub/tools/crosstool/

I'm doing everything under CentOS 6, and using one of those tools allows me to build latest kernel 
without breaking anything else.