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

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

On 22/07/16 08:52, Auger Eric wrote:
> Hi Marc,
> 
> On 22/07/2016 09:47, Marc Zyngier 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.
>>>
>>> Is there something missing on my platform or is this a general KVM ARM
>>> issue?
>>
>> This looks like a genuine bug, and I suspect this is triggered by having
>> an older QEMU that predates the explicit vgic init, hence relying on the
>> "init at first run". But in the meantime, could you dump me the bit of
>> kernel log that shows the KVM initialization, just in case I spot
>> something odd there?
> Had the same idea but QEMU v2.4.0 has the commit:
> 
> hw/intc/arm_gic: Initialize the vgic in the realize function
> (f0bb55890a173cb1e9e87d608647cac70f8f9dd4)

Fair enough. I'm (slowly) rebuilding a v2.4.0 QEMU on my A7 board, and
hopefully I'll be able to reproduce this sucker.

Thanks,

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