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

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

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?

Having compiled a 2.4.0 vintage QEMU, everything seems fine, and the
guest comes up:

maz@big-leg-emma:~$ ./qemu/build/arm-softmmu/qemu-system-arm -enable-kvm -M virt -m 512 -cpu host -nographic -serial mon:stdio -kernel /boot/zImage-test

(process:2867): GLib-WARNING **: /build/glib2.0-Ero3uS/glib2.0-2.48.0/./glib/gmem.c:483: custom memory allocation vtable not supported
[    0.000000] Booting Linux on physical CPU 0x0
[    0.000000] Linux version 4.7.0-rc7 (maz@approximate) (gcc version 5.2.1 20151005 (Linaro GCC 5.2-2015.11) ) #6281 SMP PREEMPT Fri Jul 22 10:01:56 BST 2016
[    0.000000] CPU: ARMv7 Processor [410fc074] revision 4 (ARMv7), cr=30c5387d
[    0.000000] CPU: div instructions available: patching division code
[    0.000000] CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache
[    0.000000] Machine model: linux,dummy-virt
[    0.000000] efi: Getting EFI parameters from FDT:
[    0.000000] efi: UEFI not found.
[    0.000000] Forcing write-allocate cache policy for SMP
[    0.000000] Memory policy: Data cache writealloc
[    0.000000] psci: probing for conduit method from DT.
[    0.000000] psci: PSCIv0.2 detected in firmware.
[    0.000000] psci: Using standard PSCI v0.2 function IDs
[    0.000000] psci: Trusted OS migration not required
[    0.000000] percpu: Embedded 14 pages/cpu @cfde4000 s27456 r8192 d21696 u57344
[    0.000000] Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 65024

So something is amiss somewhere else. Are you sure about the qemu
version? Built from source or packaged by a distro?

Could you send me your config? Also, can you put some traces in 
kvm_vgic_dist_init and kvm_vgic_vcpu_init, and see if they are
getting called?

Thanks,

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