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

From: Stefan Agner <stefan@agner.ch>
To: Marc Zyngier <marc.zyngier@arm.com>
Cc: kvmarm@lists.cs.columbia.edu
Subject: Re: KVM on ARM crashes with new VGIC v4.7-rc7
Date: Fri, 22 Jul 2016 01:10:54 -0700	[thread overview]
Message-ID: <5e04ab545af902ada6890653cfe09d47@agner.ch> (raw)
In-Reply-To: <5791CF97.305@arm.com>

Hi Marc,

On 2016-07-22 00:47, 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?

# dmesg | grep -C 2 kvm      
[    0.303848] RPC: Registered tcp transport module.
[    0.303880] RPC: Registered tcp NFSv4.1 backchannel transport module.
[    0.307238] kvm [1]: 8-bit VMID
[    0.307273] kvm [1]: Hyp mode initialized successfully
[    0.307713] kvm [1]: virtual timer IRQ18
[    0.312511] futex hash table entries: 512 (order: 3, 32768 bytes)
[    0.315230] workingset: timestamp_bits=28 max_order=17 bucket_order=0

--
Stefan