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: (&vcpu->mutex){+.+.+.}, at: [<d000000004225bac>]
> .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] [c0000001d08bf200] [c000000000816dd0]
> .dump_stack+0x98/0xd4 (unreliable)
> [ 143.369687] [c0000001d08bf280] [c0000000000f7058]
> .lockdep_rcu_suspicious+0x108/0x170
> [ 143.369696] [c0000001d08bf310] [d0000000042296d8]
> .kvm_io_bus_read+0x1d8/0x220 [kvm]
> [ 143.369705] [c0000001d08bf3c0] [d00000000422f980]
> .kvmppc_h_logical_ci_load+0x60/0xe0 [kvm]
Could it be that we need to srcu_read_lock(&vcpu->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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