On Wed, Oct 11, 2017 at 04:00:34PM +1100, Alexey Kardashevskiy wrote:
> kvmppc_gpa_to_ua() accesses KVM memory slot array via
> srcu_dereference_check() and this produces warnings from RCU like below.
>
> This extends the existing srcu_read_lock/unlock to cover that
> kvmppc_gpa_to_ua() as well.
>
> We did not hit this before as this lock is not needed for the realmode
> handlers and hash guests would use the realmode path all the time;
> however the radix guests are always redirected to the virtual mode
> handlers and hence the warning.
>
> [ 68.253798] ./include/linux/kvm_host.h:575 suspicious rcu_dereference_check() usage!
> [ 68.253799]
> other info that might help us debug this:
>
> [ 68.253802]
> rcu_scheduler_active = 2, debug_locks = 1
> [ 68.253804] 1 lock held by qemu-system-ppc/6413:
> [ 68.253806] #0: (&vcpu->mutex){+.+.}, at: [<c00800000e3c22f4>] vcpu_load+0x3c/0xc0 [kvm]
> [ 68.253826]
> stack backtrace:
> [ 68.253830] CPU: 92 PID: 6413 Comm: qemu-system-ppc Tainted: G W 4.14.0-rc3-00553-g432dcba58e9c-dirty #72
> [ 68.253833] Call Trace:
> [ 68.253839] [c000000fd3d9f790] [c000000000b7fcc8] dump_stack+0xe8/0x160 (unreliable)
> [ 68.253845] [c000000fd3d9f7d0] [c0000000001924c0] lockdep_rcu_suspicious+0x110/0x180
> [ 68.253851] [c000000fd3d9f850] [c0000000000e825c] kvmppc_gpa_to_ua+0x26c/0x2b0
> [ 68.253858] [c000000fd3d9f8b0] [c00800000e3e1984] kvmppc_h_put_tce+0x12c/0x2a0 [kvm]
>
> Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
Thanks, applied to my kvm-ppc-fixes branch.
Paul.
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