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

[Stefan Agner <stefan@agner.ch>]

On 2016-07-22 10:38, 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.

Same for me.

>> >
>> > 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.

Just built a mutli_v7_defconfig, fails for me too.

Isn't 32-bit ARM always using 4K pages?

--
Stefan