linux-kernel - Re: [xen-tip:linux-next 12/12] WARNING: modpost: vmlinux: section mismatch in reference: mc_debug_data+0x0 (section: .data) -> mc_debug_data

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Message-ID: <a8d89245-bcd2-41a7-9543-e517766900ba@suse.com>
Date: Thu, 27 Mar 2025 16:15:11 +0100
From: Jürgen Groß <jgross@...e.com>
To: Borislav Petkov <bp@...en8.de>
Cc: Jan Beulich <jbeulich@...e.com>, oe-kbuild-all@...ts.linux.dev,
 xen-devel@...ts.xenproject.org, Boris Ostrovsky
 <boris.ostrovsky@...cle.com>, kernel test robot <lkp@...el.com>,
 x86-ml <x86@...nel.org>, lkml <linux-kernel@...r.kernel.org>
Subject: Re: [xen-tip:linux-next 12/12] WARNING: modpost: vmlinux: section
 mismatch in reference: mc_debug_data+0x0 (section: .data) ->
 mc_debug_data_early (section: .init.data)

On 27.03.25 15:40, Borislav Petkov wrote:
> On Thu, Mar 27, 2025 at 03:21:45PM +0100, Jürgen Groß wrote:
>> Well, that is wasting nearly 3kB of the data section.
>>
>> Maybe not a big deal, but still...
> 
> We could do it until the proper fix is in place, no?
> 
> 3K is meh, especially for the hypervisor kernel, I'd say...
> 

Yeah, that was my thinking.

Another approach could be to have:

-static DEFINE_PER_CPU(struct mc_debug_data *, mc_debug_data) =
-	&mc_debug_data_early;
+static DEFINE_PER_CPU(struct mc_debug_data *, mc_debug_data);

and to use an inline access function returning &mc_debug_data_early
if the percpu variable is NULL. This access function could be __ref.

It is a debug feature after all, so having a few additional instructions
isn't the end of the world.


Juergen

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