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

[Stefan Agner <stefan@agner.ch>]

On 2016-07-22 11:11, Marc Zyngier wrote:
> On 22/07/16 18:56, Stefan Agner 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 have my own config file with the crap I need to make things work on
> the various platforms I have around. If multi_v7_defconfig works on the
> cubietruck, I'll give it a spin tomorrow. I need a beer now.
> 
>> 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...
> 
> Yeah, and that's the worrying part.


FWIW, I tried here with Qemu 2.6.0, same stack trace...

--
Stefan