Subject: Re: linux-next: build failure after merge of the tip tree

From: Ingo Molnar <[email-masked]>
Date: Wed, 14 May 2025 07:38:25 +0200

* Stephen Rothwell <[email-masked]> wrote:

> Hi all,
> 
> After merging the tip tree, today's linux-next build (x86_64 allmodconfig)
> failed like this:
> 
> In file included from drivers/net/ethernet/amd/xgbe/xgbe-dev.c:18:
> drivers/net/ethernet/amd/xgbe/xgbe-smn.h:15:10: fatal error: asm/amd_nb.h: No such file or directory
>    15 | #include <asm/amd_nb.h>
>       |          ^~~~~~~~~~~~~~
> 
> Caused by commit
> 
>   bcbb65559532 ("x86/platform/amd: Move the <asm/amd_nb.h> header to <asm/amd/nb.h>")
> 
> interacting with commit
> 
>   e49479f30ef9 ("amd-xgbe: add support for new XPCS routines")
> 
> from the net-next tree.
> 
> I have applied the following merge resolution for today.

The conflict resolution looks good to me.

Note that this is not a 'build failure in the -tip tree' per se, but a 
two-tree symmetric semantic merge conflict between the networking tree 
and the x86 tree that must be resolved at the two-tree merge level 
(-next in this case). Had you merged net-next after -tip, it would have 
triggered the build failure.

This two-tree semantic conflict should be mentioned in the pull request 
to Linus by whoever sends their tree second. (Which will likely be the 
networking tree in this particular case.)

I usually mark semantic conflicts the following way in the merge 
resolution:

    Merge branch 'x86/msr' into x86/core, to resolve conflicts
    
     Conflicts:
            arch/x86/boot/startup/sme.c
            arch/x86/coco/sev/core.c
            arch/x86/kernel/fpu/core.c
            arch/x86/kernel/fpu/xstate.c
    
     Semantic conflict:
            arch/x86/include/asm/sev-internal.h
		
Thanks,

	Ingo