linux-kernel - Re: linux-next: manual merge of the xen-tip tree with the tip tree

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Message-ID: <20170329085945.GA11382@gmail.com>
Date:   Wed, 29 Mar 2017 10:59:45 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Juergen Gross <jgross@...e.com>
Cc:     Stephen Rothwell <sfr@...b.auug.org.au>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Xen Devel <Xen-devel@...ts.xensource.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-next@...r.kernel.org, linux-kernel@...r.kernel.org,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Mathias Krause <minipli@...glemail.com>,
        Thomas Garnier <thgarnie@...gle.com>
Subject: Re: linux-next: manual merge of the xen-tip tree with the tip tree


* Juergen Gross <jgross@...e.com> wrote:

> On 29/03/17 05:35, Stephen Rothwell wrote:
> > Hi all,
> > 
> > Today's linux-next merge of the xen-tip tree got a conflict in:
> > 
> >   arch/x86/xen/enlighten.c
> > 
> > between commits:
> > 
> >   6415813bae75 ("x86/cpu: Drop wp_works_ok member of struct cpuinfo_x86")
> >   69218e47994d ("x86: Remap GDT tables in the fixmap section")
> >   b23adb7d3f7d ("x86/xen/gdt: Use X86_FEATURE_XENPV instead of globals for the GDT fixup")
> > 
> > from the tip tree and commits:
> > 
> >   75cd32d6093e ("x86/xen: split off enlighten_pv.c")
> > 
> > from the xen-tip tree.
> > 
> > I dropped the xen-tip tree for today (see other conflict reports),
> > please get together and sort these out, thanks.
> > 
> 
> Hmm, seems to be a rather bad timing for the series of Vitaly.
> 
> What is the best way to resolve those conflicts? A rebase of Vitaly's
> patches seems to be required in any case.
> 
> Should I rebase the Xen tree on current tip? This seems to be rather
> easy, but I think this will work only if I can be sure the current tip
> tree contents will all be merged by Linus before the Xen tree.

That's certainly very likely, -tip trees all go in very early in the merge window.

> I could try to cherry pick the patches from tip where Vitaly's patches
> have conflicts with, but I think this could lead to a lot of patches
> to take.

Nor is it desirable as a workflow.

I'd suggest the following: in about a week I can guarantee a working tip:x86/mm 
base with most of the 5-level paging patches applied that you could base Xen 
patches on.

Unfortunately, right now there's at least one regression with those changes that 
needs to be properly fixed before it's a suitable base tree. The fix already 
exists, it just needs to be tested and the whole tree needs to cook for a few days 
to be dependable for Xen as a base.

> Or we could delay Vitaly's series until tip has been merged, but this
> will either delay some other Xen patches depending on (or conflicting
> with) Vitaly's patches or would make the rebase for Vitaly more
> difficult.

So my suggestion would be: could you delay 75cd32d6093e for a week, and then merge 
it on top of a pulled in tip:x86/mm? I'll send that tree to Linus on the first day 
of the merge window so there shouldn't be any ordering problems.

Thanks,

	Ingo