From: David Laight <David.Laight@ACULAB.COM>
To: 'Arnd Bergmann' <arnd@arndb.de>,
Naresh Kamboju <naresh.kamboju@linaro.org>,
open list <linux-kernel@vger.kernel.org>,
linux-stable <stable@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>, "LTP List" <ltp@lists.linux.it>,
"lkft-triage@lists.linaro.org" <lkft-triage@lists.linaro.org>,
X86 ML <x86@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>,
Ingo Molnar <mingo@redhat.com>, Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Andrew Morton <akpm@linux-foundation.org>,
Dan Carpenter <dan.carpenter@linaro.org>
Subject: Re: [LTP] qemu-x86_64 compat: LTP: controllers: RIP: 0010:__alloc_pages
Date: Wed, 24 May 2023 12:54:20 +0000 [thread overview]
Message-ID: <8414a2adfee94b589458766b52f49421@AcuMS.aculab.com> (raw)
In-Reply-To: <3a055da0-fd88-4ec0-b006-9ccd382e9cc6@app.fastmail.com>
From: Arnd Bergmann
> Sent: 24 May 2023 12:18
>
> On Wed, May 24, 2023, at 11:02, Naresh Kamboju wrote:
> > While running LTP controllers following kernel crash noticed on qemu-x86_64
> > compat mode with stable-rc 6.3.4-rc2.
> >
> > Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
> >
> > Linux version 6.3.4-rc2 (tuxmake@tuxmake) (x86_64-linux-gnu-gcc
> > (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40) #1
> > SMP PREEMPT_DYNAMIC @1684862676
> > ..
> > ./runltp -f controllers
> > ...
> > cpuset_inherit 11 TPASS: cpus: Inherited information is right!
> > cpuset_inherit 13 TPASS: mems: Inherited information is right!
> > <4>[ 1130.117922] int3: 0000 [#1] PREEMPT SMP PTI
> > <4>[ 1130.118132] CPU: 0 PID: 32748 Comm: cpuset_inherit_ Not tainted
> > 6.3.4-rc2 #1
> > <4>[ 1130.118216] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009),
> > BIOS 1.14.0-2 04/01/2014
> > <4>[ 1130.118320] RIP: 0010:__alloc_pages+0xeb/0x340
> > <4>[ 1130.118605] Code: 48 c1 e0 04 48 8d 84 01 00 13 00 00 48 89 45
> > a8 8b 05 d9 31 cf 01 85 c0 0f 85 05 02 00 00 89 d8 c1 e8 03 83 e0 03
> > 89 45 c0 66 <90> 41 89 df 41 be 01 00 00 00 f6 c7 04 75 66 44 89 e6 89
> > df e8 ec
>
> I haven't figured out what is going on here, but I tracked down
> the trapping instruction <90> to the middle of the 'xchg %ax,%ax'
> two-byte nop in:
>
> ffffffff814218f4: 83 e0 03 and $0x3,%eax
> ffffffff814218f7: 89 45 c0 mov %eax,-0x40(%rbp)
> ffffffff814218fa: 66 90 xchg %ax,%ax
> ffffffff814218fc: 41 89 df mov %ebx,%r15d
> ffffffff814218ff: 41 be 01 00 00 00 mov $0x1,%r14d
>
> which in turn is the cpusets_enabled() check in prepare_alloc_pages().
Does that code actually match the call/return stack?
It is pretty much impossible to get a trap on an 0x90 byte.
I think you'd need to jump to it and then get a page fault.
So I bet that isn't the code that was actually being executed.
So either the fault address is garbage or something horrid(tm)
has happened to the page tables.
David
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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
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Mailing list info: https://lists.linux.it/listinfo/ltp
next prev parent reply other threads:[~2023-05-24 12:54 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-24 9:02 [LTP] qemu-x86_64 compat: LTP: controllers: RIP: 0010:__alloc_pages Naresh Kamboju
2023-05-24 11:18 ` Arnd Bergmann
2023-05-24 12:54 ` David Laight [this message]
2023-05-24 14:07 ` Peter Zijlstra
2023-05-24 16:09 ` Naresh Kamboju
2023-05-24 17:54 ` Peter Zijlstra
2023-05-24 20:33 ` Arnd Bergmann
2023-05-25 12:22 ` Naresh Kamboju
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