Hi,
On 25/07/16 09:17, Marc Zyngier wrote:
> On 25/07/16 09:11, Marc Zyngier wrote:
>> On 25/07/16 07:14, Stefan Agner wrote:
>>> On 2016-07-24 05:36, Marc Zyngier wrote:
>>>> On Sun, 24 Jul 2016 13:22:55 +0100
>>>> Marc Zyngier <marc.zyngier@xxxxxxx> wrote:
>>>>
>>>>> On Fri, 22 Jul 2016 10:56:44 -0700
>>>>> Stefan Agner <stefan@xxxxxxxx> 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'm now on -rc7 with multi_v7_defconfig + LPAE + KVM (and everything
>>>>> built-in to make my life simpler). The host works perfectly, and I can
>>>>> spawn VMs without any issue.
>>>>>
>>>>> I've tested with QEMU emulator version 2.2.0 (Debian 1:2.2+dfsg-5exp)
>>>>> as packaged with Jessie from a while ago. I've also upgraded the box to
>>>>> something more recent (2.5), same effect.
>>>>>
>>>>>>
>>>>>> 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...
>>>>>
>>>>> Indeed, and if these clocks were doing anything unsavoury, we'd
>>>>> probably see other things exploding. So we need to find out where we
>>>>> are diverging.
>>>>>
>>>>> What compiler are you using? I just noticed that my build
>>>>> infrastructure is a bit outdated for 32bit ARM (gcc 4.9.2), so I'm
>>>>> going to upgrade that to gcc 5.3 and retest.
>>>>
>>>> Same thing. The damn thing stubbornly works.
>>>>
>>>> Please send your full configuration, compiler version, exact QEMU
>>>> command line, and any other detail that could be vaguely relevant. As
>>>> the old VGIC gets removed in 4.8, we definitely need to nail that
>>>> sucker right now.
>>>
>>> I built the kernel with
>>> gcc-linaro-5.2-2015.11-2-x86_64_arm-linux-gnueabihf the binaries built
>>> by Linaro (full config attached). For the Rootfs (and Qemu) I did use
>>> the same compiler version, but built using OpenEmbedded.
>>>
>>> Running on a Colibri module using NXP i.MX 7Dual SoC, I haven't used it
>>> that much on mainline but it seems to be rather stable so far.
>>>
>>> I can reproduce the issue with a minimal command such as this:
>>> qemu-system-arm -enable-kvm -M virt -cpu host
>>>
>>> [ 179.430694] Unable to handle kernel paging request at virtual address
>>> fffffffc
>>> What is puzzling me a bit that the address the kernel tries to access is
>>> constantly 0xfffffffc. This would be -4, which would be -EINTR? A
>>> unhandled error return?
>>
>> Your initial report had 0xffffffe4 instead. Which looks a bit like a
>> "container_of" operation on a NULL pointer. Do you always get the same
>> backtrace? If so, any chance you could run a
>>
>> arm-linux-gnueabihf-addr2line -e vmlinux -i TheCrashingPC
>
> Actually, try with the LR value, not the PC.
I didn't see it crash, but from comparing the PC offsets of my
disassembly and Stefan's and correlating the assembly with the C code I
am quite sure it's this lock here:
static void vgic_flush_lr_state(struct kvm_vcpu *vcpu)
{
....
list_for_each_entry(irq, &vgic_cpu->ap_list_head, ap_list) }
-----> spin_lock(&irq->irq_lock);
if (unlikely(vgic_target_oracle(irq) != vcpu))
goto next;
I can see from the assembly that we would call _raw_spin_lock with -4 in
r0 if the list pointer would be NULL, which makes me wonder if we either
step on an uninitialised VCPU or if it's a bogus IRQ we are looking at?
Cheers,
Andre.
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