Re: suspicious RCU usage with kvm_pr

2015-09-18 Thread Denis Kirjanov 
On 9/18/15, Thomas Huth  wrote:
> On 16/09/15 12:59, Denis Kirjanov wrote:
>> On 9/16/15, Thomas Huth  wrote:
>>> On 16/09/15 10:51, Denis Kirjanov wrote:
 Hi,

 I see the following trace on qemu startup (ps700 blade):

 v4.2-11169-g64d1def


 [  143.369638] ===
 [  143.369640] [ INFO: suspicious RCU usage. ]
 [  143.369643] 4.2.0-11169-g64d1def #10 Tainted: G S
 [  143.369645] ---
 [  143.369647] arch/powerpc/kvm/../../../virt/kvm/kvm_main.c:3310
 suspicious rcu_dereference_check() usage!
 [  143.369649]
 other info that might help us debug this:

 [  143.369652]
 rcu_scheduler_active = 1, debug_locks = 1
 [  143.369655] 1 lock held by qemu-system-ppc/2292:
 [  143.369656]  #0:  (>mutex){+.+.+.}, at: []
 .vcpu_load+0x2c/0xb0 [kvm]
 [  143.369672]
 stack backtrace:
 [  143.369675] CPU: 12 PID: 2292 Comm: qemu-system-ppc Tainted: G S
   4.2.0-11169-g64d1def #10
 [  143.369677] Call Trace:
 [  143.369682] [c001d08bf200] [c0816dd0]
 .dump_stack+0x98/0xd4 (unreliable)
 [  143.369687] [c001d08bf280] [c00f7058]
 .lockdep_rcu_suspicious+0x108/0x170
 [  143.369696] [c001d08bf310] [d42296d8]
 .kvm_io_bus_read+0x1d8/0x220 [kvm]
 [  143.369705] [c001d08bf3c0] [d422f980]
 .kvmppc_h_logical_ci_load+0x60/0xe0 [kvm]
>>>
>>> Could it be that we need to srcu_read_lock(>kvm->srcu) before
>>> calling the kvm_io_bus_read/write() function in the
>>> kvmppc_h_logical_ci_load/store() function?
>>
>> I haven't had time to dig into this. I'll try it.
>
> FYI, I had the same problem with kvm_hv, so I tried to come up with a
> patch:
>
>   https://patchwork.ozlabs.org/patch/519143/
>
> Sorry, forgot to CC: you there, but it would be great if you could give
> it a try!

It fixed the issue. Thanks!

>
>  Thomas
>
>
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Re: suspicious RCU usage with kvm_pr

2015-09-18 Thread Thomas Huth 
On 16/09/15 12:59, Denis Kirjanov wrote:
> On 9/16/15, Thomas Huth  wrote:
>> On 16/09/15 10:51, Denis Kirjanov wrote:
>>> Hi,
>>>
>>> I see the following trace on qemu startup (ps700 blade):
>>>
>>> v4.2-11169-g64d1def
>>>
>>>
>>> [  143.369638] ===
>>> [  143.369640] [ INFO: suspicious RCU usage. ]
>>> [  143.369643] 4.2.0-11169-g64d1def #10 Tainted: G S
>>> [  143.369645] ---
>>> [  143.369647] arch/powerpc/kvm/../../../virt/kvm/kvm_main.c:3310
>>> suspicious rcu_dereference_check() usage!
>>> [  143.369649]
>>> other info that might help us debug this:
>>>
>>> [  143.369652]
>>> rcu_scheduler_active = 1, debug_locks = 1
>>> [  143.369655] 1 lock held by qemu-system-ppc/2292:
>>> [  143.369656]  #0:  (>mutex){+.+.+.}, at: []
>>> .vcpu_load+0x2c/0xb0 [kvm]
>>> [  143.369672]
>>> stack backtrace:
>>> [  143.369675] CPU: 12 PID: 2292 Comm: qemu-system-ppc Tainted: G S
>>>   4.2.0-11169-g64d1def #10
>>> [  143.369677] Call Trace:
>>> [  143.369682] [c001d08bf200] [c0816dd0]
>>> .dump_stack+0x98/0xd4 (unreliable)
>>> [  143.369687] [c001d08bf280] [c00f7058]
>>> .lockdep_rcu_suspicious+0x108/0x170
>>> [  143.369696] [c001d08bf310] [d42296d8]
>>> .kvm_io_bus_read+0x1d8/0x220 [kvm]
>>> [  143.369705] [c001d08bf3c0] [d422f980]
>>> .kvmppc_h_logical_ci_load+0x60/0xe0 [kvm]
>>
>> Could it be that we need to srcu_read_lock(>kvm->srcu) before
>> calling the kvm_io_bus_read/write() function in the
>> kvmppc_h_logical_ci_load/store() function?
> 
> I haven't had time to dig into this. I'll try it.

FYI, I had the same problem with kvm_hv, so I tried to come up with a patch:

https://patchwork.ozlabs.org/patch/519143/

Sorry, forgot to CC: you there, but it would be great if you could give
it a try!

 Thomas

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suspicious RCU usage with kvm_pr

2015-09-16 Thread Denis Kirjanov 
Hi,

I see the following trace on qemu startup (ps700 blade):

v4.2-11169-g64d1def


[  143.369638] ===
[  143.369640] [ INFO: suspicious RCU usage. ]
[  143.369643] 4.2.0-11169-g64d1def #10 Tainted: G S
[  143.369645] ---
[  143.369647] arch/powerpc/kvm/../../../virt/kvm/kvm_main.c:3310
suspicious rcu_dereference_check() usage!
[  143.369649]
other info that might help us debug this:

[  143.369652]
rcu_scheduler_active = 1, debug_locks = 1
[  143.369655] 1 lock held by qemu-system-ppc/2292:
[  143.369656]  #0:  (>mutex){+.+.+.}, at: []
.vcpu_load+0x2c/0xb0 [kvm]
[  143.369672]
stack backtrace:
[  143.369675] CPU: 12 PID: 2292 Comm: qemu-system-ppc Tainted: G S
  4.2.0-11169-g64d1def #10
[  143.369677] Call Trace:
[  143.369682] [c001d08bf200] [c0816dd0]
.dump_stack+0x98/0xd4 (unreliable)
[  143.369687] [c001d08bf280] [c00f7058]
.lockdep_rcu_suspicious+0x108/0x170
[  143.369696] [c001d08bf310] [d42296d8]
.kvm_io_bus_read+0x1d8/0x220 [kvm]
[  143.369705] [c001d08bf3c0] [d422f980]
.kvmppc_h_logical_ci_load+0x60/0xe0 [kvm]
[  143.369712] [c001d08bf450] [d42d8d30]
.kvmppc_h_pr+0x4f0/0xc80 [kvm_pr]
[  143.369718] [c001d08bf570] [d42d9a30]
.kvmppc_core_emulate_op_pr+0x270/0x720 [kvm_pr]
[  143.369723] [c001d08bf630] [d42d0684]
.kvmppc_emulate_instruction+0xd4/0x7c0 [kvm_pr]
[  143.369728] [c001d08bf6f0] [d42d82f8]
.kvmppc_handle_exit_pr+0xc98/0xf80 [kvm_pr]
[  143.369734] [c001d08bf790] [d42dab2c]
after_sprg3_load+0x88/0x98 [kvm_pr]
[  143.369739] [c001d08bf960] [d42d742c]
.kvmppc_vcpu_run_pr+0xdc/0x190 [kvm_pr]
[  143.369748] [c001d08bf9f0] [d423114c]
.kvmppc_vcpu_run+0x2c/0x40 [kvm]
[  143.369756] [c001d08bfa60] [d422e4b4]
.kvm_arch_vcpu_ioctl_run+0x54/0x170 [kvm]
[  143.369764] [c001d08bfaf0] [d4226298]
.kvm_vcpu_ioctl+0x5f8/0x8b0 [kvm]
[  143.369768] [c001d08bfcb0] [c0297c24] .do_vfs_ioctl+0x4d4/0x820
[  143.369771] [c001d08bfd90] [c0297fc8] .SyS_ioctl+0x58/0xb0
[  143.369775] [c001d08bfe30] [c000916c] system_call+0x38/0xd0
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Re: suspicious RCU usage with kvm_pr

2015-09-16 Thread Denis Kirjanov 
On 9/16/15, Thomas Huth  wrote:
> On 16/09/15 10:51, Denis Kirjanov wrote:
>> Hi,
>>
>> I see the following trace on qemu startup (ps700 blade):
>>
>> v4.2-11169-g64d1def
>>
>>
>> [  143.369638] ===
>> [  143.369640] [ INFO: suspicious RCU usage. ]
>> [  143.369643] 4.2.0-11169-g64d1def #10 Tainted: G S
>> [  143.369645] ---
>> [  143.369647] arch/powerpc/kvm/../../../virt/kvm/kvm_main.c:3310
>> suspicious rcu_dereference_check() usage!
>> [  143.369649]
>> other info that might help us debug this:
>>
>> [  143.369652]
>> rcu_scheduler_active = 1, debug_locks = 1
>> [  143.369655] 1 lock held by qemu-system-ppc/2292:
>> [  143.369656]  #0:  (>mutex){+.+.+.}, at: []
>> .vcpu_load+0x2c/0xb0 [kvm]
>> [  143.369672]
>> stack backtrace:
>> [  143.369675] CPU: 12 PID: 2292 Comm: qemu-system-ppc Tainted: G S
>>   4.2.0-11169-g64d1def #10
>> [  143.369677] Call Trace:
>> [  143.369682] [c001d08bf200] [c0816dd0]
>> .dump_stack+0x98/0xd4 (unreliable)
>> [  143.369687] [c001d08bf280] [c00f7058]
>> .lockdep_rcu_suspicious+0x108/0x170
>> [  143.369696] [c001d08bf310] [d42296d8]
>> .kvm_io_bus_read+0x1d8/0x220 [kvm]
>> [  143.369705] [c001d08bf3c0] [d422f980]
>> .kvmppc_h_logical_ci_load+0x60/0xe0 [kvm]
>
> Could it be that we need to srcu_read_lock(>kvm->srcu) before
> calling the kvm_io_bus_read/write() function in the
> kvmppc_h_logical_ci_load/store() function?

I haven't had time to dig into this. I'll try it.

Thanks

>
>  Thomas
>
>
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Re: suspicious RCU usage with kvm_pr

2015-09-16 Thread Thomas Huth 
On 16/09/15 10:51, Denis Kirjanov wrote:
> Hi,
> 
> I see the following trace on qemu startup (ps700 blade):
> 
> v4.2-11169-g64d1def
> 
> 
> [  143.369638] ===
> [  143.369640] [ INFO: suspicious RCU usage. ]
> [  143.369643] 4.2.0-11169-g64d1def #10 Tainted: G S
> [  143.369645] ---
> [  143.369647] arch/powerpc/kvm/../../../virt/kvm/kvm_main.c:3310
> suspicious rcu_dereference_check() usage!
> [  143.369649]
> other info that might help us debug this:
> 
> [  143.369652]
> rcu_scheduler_active = 1, debug_locks = 1
> [  143.369655] 1 lock held by qemu-system-ppc/2292:
> [  143.369656]  #0:  (>mutex){+.+.+.}, at: []
> .vcpu_load+0x2c/0xb0 [kvm]
> [  143.369672]
> stack backtrace:
> [  143.369675] CPU: 12 PID: 2292 Comm: qemu-system-ppc Tainted: G S
>   4.2.0-11169-g64d1def #10
> [  143.369677] Call Trace:
> [  143.369682] [c001d08bf200] [c0816dd0]
> .dump_stack+0x98/0xd4 (unreliable)
> [  143.369687] [c001d08bf280] [c00f7058]
> .lockdep_rcu_suspicious+0x108/0x170
> [  143.369696] [c001d08bf310] [d42296d8]
> .kvm_io_bus_read+0x1d8/0x220 [kvm]
> [  143.369705] [c001d08bf3c0] [d422f980]
> .kvmppc_h_logical_ci_load+0x60/0xe0 [kvm]

Could it be that we need to srcu_read_lock(>kvm->srcu) before
calling the kvm_io_bus_read/write() function in the
kvmppc_h_logical_ci_load/store() function?

 Thomas

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