Subject: Re: linux-next: manual merge of the kvm tree

From: Hollis Blanchard <[email-masked]>
Date: Mon, 22 Dec 2008 19:02:31 -0600

On Tue, 2008-12-23 at 11:07 +1100, Paul Mackerras wrote:
> Hollis Blanchard writes:
> 
> > On Tue, 2008-12-23 at 09:29 +1100, Paul Mackerras wrote:
> > > Hollis Blanchard writes:
> > > 
> > > > > Patch is in Paulus -next already so we'll have to do a manual resolve.
> > > > 
> > > > Who has to do it? My code should "win".
> > > 
> > > Do you have your own tree or is all your stuff in the main kvm tree?
> > > 
> > > If there is a powerpc KVM tree, I could pull that and resolve the
> > > conflict, but I don't want to pull all the queued up KVM stuff.
> > 
> > It's just the main KVM tree.
> > 
> > > Worst case is Linus gets to resolve the conflict in the merge window.
> > > If that's just a matter of him taking your version of the file, it
> > > should be within his powers to manage. :)
> > 
> > Yeah, that's what I meant by "win"... whatever changes Ben made are to
> > now-dead code, so the code in kvm.git should be used. Does Linus need
> > special instruction to do this, or how does that work?
> 
> ppc44x_defconfig now fails to build in my tree because of _tlbil_all
> being undefined (it has CONFIG_KVM=y), so I need some sort of fix.
> What would happen if I made arch/powerpc/kvm/powerpc.c look like the
> version from the KVM tree?

It still wouldn't build, because it would require new functions (e.g.
kvmppc_core_vcpu_put) to be defined in other files.

I don't really know what to say, because from my point of view the
offending code was removed a long time ago, so it shouldn't be causing
these problems. In hindsight, what is the best solution in these
situations? Maybe if Ben had talked to me we could have applied the
exact same patch to powerpc.git and kvm.git at the same time, which
would keep both trees building and still be automatically merged later.

If you commit a new change to your tree that reverses only the
arch/powerpc/kvm/powerpc.c part of Ben's patch, would that solve the
merge problem? ppc44x_defconfig would still fail in the meantime though.
If you fix the ppc44x_defconfig build, the merge problem is compounded.
Either way I guess it is something that needs to be sorted out in
powerpc.git, so you can pick which style of breakage you'd prefer?

-- 
Hollis Blanchard
IBM Linux Technology Center