Re: [PATCH] mapletree-vs-khugepaged

From: Liam Howlett <liam.howlett@oracle.com>
To: Heiko Carstens <hca@linux.ibm.com>
Cc: Guenter Roeck <linux@roeck-us.net>,
	Andrew Morton <akpm@linux-foundation.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mapletree-vs-khugepaged
Date: Fri, 29 Apr 2022 16:18:23 +0000	[thread overview]
Message-ID: <20220429161813.oe55p4akkinjcarq@revolver> (raw)
In-Reply-To: <Ymvjt7GEXE306WyE@osiris>

* Heiko Carstens <hca@linux.ibm.com> [220429 09:19]:
> On Fri, Apr 29, 2022 at 01:01:53PM +0000, Liam Howlett wrote:
> > * Heiko Carstens <hca@linux.ibm.com> [220429 08:10]:
> > > On Thu, Apr 28, 2022 at 10:20:40AM -0700, Guenter Roeck wrote:
> > > > On Wed, Apr 27, 2022 at 03:10:45PM -0700, Andrew Morton wrote:
> > > > > Fix mapletree for patch series "Make khugepaged collapse readonly FS THP
> > > > > more consistent", v3.
> > > > > 
> > > > > Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
> > > > > Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> > > > 
> > > > This patch causes all my sparc64 boot tests to fail. Bisect and crash logs
> > > > attached.
> > > > 
> > > > Guenter
> ...
> > > 
> > > FWIW, same on s390 - linux-next is completely broken. Note: I didn't
> > > bisect, but given that the call trace, and even the failing address
> > > match, I'm quite confident it is the same reason.
> > 
> > This is worth a lot to me.  Thanks for the report and the testing.
> 
> Not sure if it is of any relevance, and you are probably aware if it
> anyway, but both sparc64 and s390 are big endian; and there was no
> report from little endian architectures yet.

I was aware they are big endian, but thanks - the more info the better.
sparc64 is technically bi-endian but I think everyone runs it in big
endian mode?  Is alpha the same?  There was a report of alpha having
issues too. m68k is also big endian - but also nommu, so that makes
testing difficult.

What I liked about the s390 report is that the s390 is very good at
finding vma issues since it seems to use move_vma (among others) a lot
more than other arch. I've built my maple tree + v5.18-rc2 and
successfully booted with KASAN and poison on the s390. Andrew asked me
to respin maple on top of one of his branches with the fixes rolled in
so I'm going to work on that while the m68k buildroot compiles.

In parallel, I'm running a (very slow qemu) install of sparc64 and
trying to figure out how to get a qemu setup for those. I'm trying to
follow what Guenter has in his repo[1] and have found debian ISOs[2]
that may help with some of these targets.

1. https://github.com/groeck/linux-build-test
2. https://cdimage.debian.org/cdimage/ports/snapshots/