Re: KVM on ARM crashes with new VGIC v4.7-rc7

[Marc Zyngier <marc.zyngier@arm.com>]

On 25/07/16 09:11, Marc Zyngier wrote:
> On 25/07/16 07:14, Stefan Agner wrote:
>> On 2016-07-24 05:36, Marc Zyngier wrote:
>>> On Sun, 24 Jul 2016 13:22:55 +0100
>>> Marc Zyngier <marc.zyngier@arm.com> wrote:
>>>
>>>> On Fri, 22 Jul 2016 10:56:44 -0700
>>>> Stefan Agner <stefan@agner.ch> wrote:
>>>>
>>>>> On 2016-07-22 10:49, Marc Zyngier wrote:
>>>>>> On 22/07/16 18:38, Andrew Jones wrote:
>>>>>>> On Fri, Jul 22, 2016 at 04:40:15PM +0100, Marc Zyngier wrote:
>>>>>>>> On 22/07/16 15:35, Andrew Jones wrote:
>>>>>>>>> On Fri, Jul 22, 2016 at 11:42:02AM +0100, Andre Przywara wrote:
>>>>>>>>>> Hi Stefan,
>>>>>>>>>>
>>>>>>>>>> On 22/07/16 06:57, Stefan Agner wrote:
>>>>>>>>>>> Hi,
>>>>>>>>>>>
>>>>>>>>>>> I tried KVM on a Cortex-A7 platform (i.MX 7Dual SoC) and encountered
>>>>>>>>>>> this stack trace immediately after invoking qemu-system-arm:
>>>>>>>>>>>
>>>>>>>>>>> Unable to handle kernel paging request at virtual address ffffffe4
>>>>>>>>>>> pgd = 8ca52740
>>>>>>>>>>> [ffffffe4] *pgd=80000080007003, *pmd=8ff7e003, *pte=00000000
>>>>>>>>>>> Internal error: Oops: 207 [#1] SMP ARM
>>>>>>>>>>> Modules linked in:
>>>>>>>>>>> CPU: 0 PID: 329 Comm: qemu-system-arm Tainted: G        W
>>>>>>>>>>> 4.7.0-rc7-00094-gea3ed2c #109
>>>>>>>>>>> Hardware name: Freescale i.MX7 Dual (Device Tree)
>>>>>>>>>>> task: 8ca3ee40 ti: 8d2b0000 task.ti: 8d2b0000
>>>>>>>>>>> PC is at do_raw_spin_lock+0x8/0x1dc
>>>>>>>>>>> LR is at kvm_vgic_flush_hwstate+0x8c/0x224
>>>>>>>>>>> pc : [<8027c87c>]    lr : [<802172d4>]    psr: 60070013
>>>>>>>>>>> sp : 8d2b1e38  ip : 8d2b0000  fp : 00000001
>>>>>>>>>>> r10: 8d2b0000  r9 : 00010000  r8 : 8d2b8e54
>>>>>>>>>>> fec 30be0000.ethernet eth0: MDIO read timeout
>>>>>>>>>>> r7 : 8d2b8000  r6 : 8d2b8e74  r5 : 00000000  r4 : ffffffe0
>>>>>>>>>>> r3 : 00004ead  r2 : 00000000  r1 : 00000000  r0 : ffffffe0
>>>>>>>>>>> Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
>>>>>>>>>>> Control: 30c5387d  Table: 8ca52740  DAC: fffffffd
>>>>>>>>>>> Process qemu-system-arm (pid: 329, stack limit = 0x8d2b0210)
>>>>>>>>>>> Stack: (0x8d2b1e38 to 0x8d2b2000)
>>>>>>>>>>> 1e20:                                                       ffffffe0
>>>>>>>>>>> 00000000
>>>>>>>>>>> 1e40: 8d2b8e74 8d2b8000 8d2b8e54 00010000 8d2b0000 802172d4 8d2b8000
>>>>>>>>>>> 810074f8
>>>>>>>>>>> 1e60: 81007508 8ca5f800 8d284000 00010000 8d2b0000 8020fbd4 8ce9a000
>>>>>>>>>>> 8ca5f800
>>>>>>>>>>> 1e80: 00000000 00010000 00000000 00ff0000 8d284000 00000000 00000000
>>>>>>>>>>> 7ffbfeff
>>>>>>>>>>> 1ea0: fffffffe 00000000 8d28b780 00000000 755fec6c 00000000 00000000
>>>>>>>>>>> ffffe000
>>>>>>>>>>> 1ec0: 8d2b8000 00000000 8d28b780 00000000 755fec6c 8020af90 00000000
>>>>>>>>>>> 8023f248
>>>>>>>>>>> 1ee0: 0000000a 755fe98c 8d2b1f08 00000008 8021aa84 ffffe000 00000000
>>>>>>>>>>> 00000000
>>>>>>>>>>> 1f00: 8a00d860 8d28b780 80334f94 00000000 8d2b0000 80334748 00000000
>>>>>>>>>>> 00000000
>>>>>>>>>>> 1f20: 00000000 8d28b780 00004000 00000009 8d28b500 00000024 8104ebee
>>>>>>>>>>> 80bc2ec4
>>>>>>>>>>> 1f40: 80bafa24 8034138c 00000000 00000000 80341248 00000000 755fec6c
>>>>>>>>>>> 007c1e70
>>>>>>>>>>> 1f60: 00000009 00004258 0000ae80 8d28b781 00000009 8d28b780 0000ae80
>>>>>>>>>>> 00000000
>>>>>>>>>>> 1f80: 8d2b0000 00000000 755fec6c 80334f94 007c1e70 322a7400 00004258
>>>>>>>>>>> 00000036
>>>>>>>>>>> 1fa0: 8021aa84 8021a900 007c1e70 322a7400 00000009 0000ae80 00000000
>>>>>>>>>>> 755feac0
>>>>>>>>>>> 1fc0: 007c1e70 322a7400 00004258 00000036 7e9aff58 01151da4 76f8b4c0
>>>>>>>>>>> 755fec6c
>>>>>>>>>>> 1fe0: 0038192c 755fea9c 00048ae7 7697d66c 60070010 00000009 00000000
>>>>>>>>>>> 00000000
>>>>>>>>>>> [<8027c87c>] (do_raw_spin_lock) from [<802172d4>]
>>>>>>>>>>> (kvm_vgic_flush_hwstate+0x8c/0x224)
>>>>>>>>>>> [<802172d4>] (kvm_vgic_flush_hwstate) from [<8020fbd4>]
>>>>>>>>>>> (kvm_arch_vcpu_ioctl_run+0x110/0x478)
>>>>>>>>>>> [<8020fbd4>] (kvm_arch_vcpu_ioctl_run) from [<8020af90>]
>>>>>>>>>>> (kvm_vcpu_ioctl+0x2e0/0x6d4)
>>>>>>>>>>> [<8020af90>] (kvm_vcpu_ioctl) from [<80334748>]
>>>>>>>>>>> (do_vfs_ioctl+0xa0/0x8b8)
>>>>>>>>>>> [<80334748>] (do_vfs_ioctl) from [<80334f94>] (SyS_ioctl+0x34/0x5c)
>>>>>>>>>>> [<80334f94>] (SyS_ioctl) from [<8021a900>] (ret_fast_syscall+0x0/0x1c)
>>>>>>>>>>> Code: e49de004 ea09ea24 e92d47f0 e3043ead (e5902004)
>>>>>>>>>>> ---[ end trace cb88537fdc8fa206 ]---
>>>>>>>>>>>
>>>>>>>>>>> I use CONFIG_KVM_NEW_VGIC=y. This happens to me with a rather minimal
>>>>>>>>>>> qemu invocation (qemu-system-arm -enable-kvm -M virt -cpu host
>>>>>>>>>>> -nographic -serial stdio -kernel zImage).
>>>>>>>>>>>
>>>>>>>>>>> Using a bit older Qemu version 2.4.0.
>>>>>>>>>>
>>>>>>>>>> I just tried with a self compiled QEMU 2.4.0 and the Ubuntu 14.04
>>>>>>>>>> provided 2.0.0, it worked fine with Linus' current HEAD as a host kernel
>>>>>>>>>> on a Midway (Cortex-A15).
>>>>>>>>>
>>>>>>>>> I can reproduce the issue with a latest QEMU build on AMD Seattle
>>>>>>>>> (I haven't tried anywhere else yet)
>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Can you try to disable the new VGIC, just to see if that's a regression?
>>>>>>>>>
>>>>>>>>> Disabling NEW_VGIC "fixes" guest boots.
>>>>>>>>>
>>>>>>>>> I'm not using defconfig for my host kernel. I'll do a couple more
>>>>>>>>> tests and provide a comparison of my config vs. a defconfig in
>>>>>>>>> a few minutes.
>>>>>>>>
>>>>>>>> Damn. It is not failing for me, so it has to be a kernel config thing...
>>>>>>>> If you can narrow it down to the difference with defconfig, that'd be
>>>>>>>> tremendously helpful.
>>>>>>>
>>>>>>> It's PAGE_SIZE; 64K doesn't work, 4K does, regardless of VA_BITS
>>>>>>> selection.
>>>>>>
>>>>>> That definitely doesn't match Stefan's report (32bit only has 4k). I'll
>>>>>
>>>>> Hehe, was just plowing through code and came to that conclusion, glad I
>>>>> got that right :-)
>>>>>
>>>>> What defconfig do you use? I could reproduce the issue also with
>>>>> multi_v7_defconfig + ARM_LPAE + KVM.
>>>>
>>>> I'm now on -rc7 with multi_v7_defconfig + LPAE + KVM (and everything
>>>> built-in to make my life simpler). The host works perfectly, and I can
>>>> spawn VMs without any issue.
>>>>
>>>> I've tested with QEMU emulator version 2.2.0 (Debian 1:2.2+dfsg-5exp)
>>>> as packaged with Jessie from a while ago. I've also upgraded the box to
>>>> something more recent (2.5), same effect.
>>>>
>>>>>
>>>>> Btw, I am not exactly on vanilla 4.7-rc7, I merged Shawns for-next +
>>>>> clock next to get to the bits and pieces required for my board...
>>>>>
>>>>> That said, it works fine otherwise, and the stacktrace looks rather
>>>>> platform independent...
>>>>
>>>> Indeed, and if these clocks were doing anything unsavoury, we'd
>>>> probably see other things exploding. So we need to find out where we
>>>> are diverging.
>>>>
>>>> What compiler are you using? I just noticed that my build
>>>> infrastructure is a bit outdated for 32bit ARM (gcc 4.9.2), so I'm
>>>> going to upgrade that to gcc 5.3 and retest.
>>>
>>> Same thing. The damn thing stubbornly works.
>>>
>>> Please send your full configuration, compiler version, exact QEMU
>>> command line, and any other detail that could be vaguely relevant. As
>>> the old VGIC gets removed in 4.8, we definitely need to nail that
>>> sucker right now.
>>
>> I built the kernel with
>> gcc-linaro-5.2-2015.11-2-x86_64_arm-linux-gnueabihf the binaries built
>> by Linaro (full config attached). For the Rootfs (and Qemu) I did use
>> the same compiler version, but built using OpenEmbedded.
>>
>> Running on a Colibri module using NXP i.MX 7Dual SoC, I haven't used it
>> that much on mainline but it seems to be rather stable so far.
>>
>> I can reproduce the issue with a minimal command such as this:
>> qemu-system-arm -enable-kvm -M virt -cpu host
>>
>> [  179.430694] Unable to handle kernel paging request at virtual address
>> fffffffc
>> What is puzzling me a bit that the address the kernel tries to access is
>> constantly 0xfffffffc. This would be -4, which would be -EINTR? A
>> unhandled error return?
> 
> Your initial report had 0xffffffe4 instead. Which looks a bit like a
> "container_of" operation on a NULL pointer. Do you always get the same
> backtrace? If so, any chance you could run a
> 
> arm-linux-gnueabihf-addr2line -e vmlinux -i TheCrashingPC

Actually, try with the LR value, not the PC.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...