linux-kernel - Re: Purgatory compile flag changes apparently causing Kexec relocation overflows

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Message-ID: <20190829143305.GD29967@swahl-linux>
Date:   Thu, 29 Aug 2019 09:33:05 -0500
From:   Steve Wahl <steve.wahl@....com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Steve Wahl <steve.wahl@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>, russ.anderson@....com,
        dimitri.sivanich@....com, mike.travis@....com
Subject: Re: Purgatory compile flag changes apparently causing Kexec
 relocation overflows

On Wed, Aug 28, 2019 at 03:22:13PM -0700, Nick Desaulniers wrote:
> 
> One point that might be more useful first would be, is a revert of:
> 
> commit b059f801a937 ("x86/purgatory: Use CFLAGS_REMOVE rather than
> reset KBUILD_CFLAGS")
> 
> good enough, or must:
> 
> commit 4ce97317f41d ("x86/purgatory: Do not use __builtin_memcpy and
> __builtin_memset")
> 
> be reverted additionally?  They were part of a 2 patch patchset.  I
> would prefer tglx to revert as few patches as necessary if possible
> (to avoid "revert of revert" soup), and I doubt the latter patch needs
> to be reverted.  (Even more preferential would be a fix, with no
> reverts, but whichever).

A revert of the single commit is sufficient.  Previously I have
checked out and compiled the tree at commit b059f801a937 and
b059f801a937^ (with caret, the previous commit).  It worked with the
previous commit, but not with b059f801a937.

4ce97317f41d *is* the previous commit to b059f801a937, so it was in
both kernels that I tested:

$ git log -1 --oneline b059f801a937^ | cat
4ce97317f41d x86/purgatory: Do not use __builtin_memcpy and __builtin_memset
$ 

And, I also did an exploratory 'git revert b059f801a937' at the tip of
the tree.  That corrects the problem as well.

So both say that it's only the single commit that would need to be
reverted *if* that's the route taken.

Now, on to seeing if we can narrow this down to a fix with no reverts
instead.

--> Steve
-- 
Steve Wahl, Hewlett Packard Enterprise