linux-kernel - Re: qemu-arm64: CONFIG_ARM64_64K_PAGES=y kernel crash on qemu-arm64 with Linux next-20241210 and above

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Message-ID: <a3406049-7ab5-45b9-80bf-46f73ef73a4f@stanley.mountain>
Date: Thu, 19 Dec 2024 18:10:56 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Qu Wenruo <quwenruo.btrfs@....com>
Cc: Naresh Kamboju <naresh.kamboju@...aro.org>, qemu-devel@...gnu.org,
	open list <linux-kernel@...r.kernel.org>,
	Linux Regressions <regressions@...ts.linux.dev>,
	linux-ext4 <linux-ext4@...r.kernel.org>,
	lkft-triage@...ts.linaro.org, linux-mm <linux-mm@...ck.org>,
	Linux btrfs <linux-btrfs@...r.kernel.org>,
	Alex Bennée <alex.bennee@...aro.org>,
	Anders Roxell <anders.roxell@...aro.org>,
	Arnd Bergmann <arnd@...db.de>, Qu Wenruo <wqu@...e.com>,
	David Sterba <dsterba@...e.com>
Subject: Re: qemu-arm64: CONFIG_ARM64_64K_PAGES=y kernel crash on qemu-arm64
 with Linux next-20241210 and above

On Thu, Dec 19, 2024 at 10:44:12AM +1030, Qu Wenruo wrote:
> 
> 
> 在 2024/12/19 06:37, Qu Wenruo 写道:
> > 
> > 
> > 在 2024/12/19 02:22, Naresh Kamboju 写道:
> > > On Wed, 18 Dec 2024 at 17:33, Naresh Kamboju
> > > <naresh.kamboju@...aro.org> wrote:
> > > > 
> > > > The following kernel crash noticed on qemu-arm64 while running the
> > > > Linux next-20241210 tag (to next-20241218) kernel built with
> > > >   - CONFIG_ARM64_64K_PAGES=y
> > > >   - CONFIG_ARM64_16K_PAGES=y
> > > > and running LTP smoke tests.
> > > > 
> > > > First seen on Linux next-20241210.
> > > >    Good: next-20241209
> > > >    Bad:  next-20241210 and next-20241218
> > > > 
> > > > qemu-arm64: 9.1.2
> > > > 
> > > > Anyone noticed this ?
> > > > 
> > > 
> > > Anders bisected this reported regression and found,
> > > # first bad commit:
> > >    [9c1d66793b6faa00106ae4c866359578bfc012d2]
> > >    btrfs: validate system chunk array at btrfs_validate_super()
> > 
> > Weird, I run daily fstests with 64K page sized aarch64 VM.
> > 
> > But never hit a crash on this.
> > 
> > And the original crash call trace only points back to ext4, not btrfs.
> > 

Yeah.  But it's in the memory allocator so it looks like memory
corruption.  After the ext4 crash then random other stuff starts
crashing as well when it allocates memory.

> > Mind to test it with KASAN enabled?
> 

Anders is going to try that later and report back.

> Another thing is, how do you enable both 16K and 64K page size at the
> same time?
> 
> The Kconfig should only select one page size IIRC.

Right.  We tested 4k, 16k and 64k.  4k pages worked.

> 
> And for the bisection, does it focus on the test failure or the crash?
> 

The crash.

regards,
dan carpenter