On 10/12/2015 17:53, Borislav Petkov wrote:
> Just did, there it splats even when booting the guest, without even
> injecting NMIs:
>
> [ 113.233992] ===============================
> [ 113.238192] [ INFO: suspicious RCU usage. ]
> [ 113.242393] 4.4.0-rc4+ #1 Not tainted
> [ 113.246056] -------------------------------
> [ 113.250257] arch/x86/kvm/trace.h:29 suspicious rcu_dereference_check() usage!
> [ 113.257400]
> other info that might help us debug this:
>
> [ 113.265432]
> RCU used illegally from idle CPU!
> rcu_scheduler_active = 1, debug_locks = 0
> [ 113.276321] RCU used illegally from extended quiescent state!
> [ 113.282083] 1 lock held by qemu-system-x86/2275:
> [ 113.286711] #0: (&vcpu->mutex){+.+.+.}, at: [<ffffffffa01d472c>] vcpu_load+0x1c/0x80 [kvm]
> [ 113.295270]
> stack backtrace:
> [ 113.299644] CPU: 4 PID: 2275 Comm: qemu-system-x86 Not tainted 4.4.0-rc4+ #1
> [ 113.306706] Hardware name: Dell Inc. Precision T3600/0PTTT9, BIOS A13 05/11/2014
> [ 113.314122] 0000000000000001 ffff88042f263d28 ffffffff813c2cfc ffff880432d53000
> [ 113.321575] ffff88042f263d58 ffffffff810c5157 ffff88042f268000 0000000000000000
> [ 113.329027] 0000000000000000 0000000000000001 ffff88042f263e10 ffffffffa01ee7c8
> [ 113.336483] Call Trace:
> [ 113.338939] [<ffffffff813c2cfc>] dump_stack+0x4e/0x82
> [ 113.344098] [<ffffffff810c5157>] lockdep_rcu_suspicious+0xe7/0x120
> [ 113.350385] [<ffffffffa01ee7c8>] kvm_arch_vcpu_ioctl_run+0x16f8/0x19c0 [kvm]
> [ 113.357544] [<ffffffffa01ed1a0>] ? kvm_arch_vcpu_ioctl_run+0xd0/0x19c0 [kvm]
> [ 113.364695] [<ffffffffa01d4b32>] kvm_vcpu_ioctl+0x342/0x700 [kvm]
> [ 113.370896] [<ffffffff810c4a7d>] ? __lock_is_held+0x4d/0x70
> [ 113.376583] [<ffffffff812351ae>] ? __fget+0xfe/0x200
> [ 113.381662] [<ffffffff812291f1>] do_vfs_ioctl+0x301/0x550
> [ 113.387156] [<ffffffff8123531a>] ? __fget_light+0x2a/0x90
> [ 113.392654] [<ffffffff81229481>] SyS_ioctl+0x41/0x70
> [ 113.397739] [<ffffffff8185cb36>] entry_SYSCALL_64_fastpath+0x16/0x7a
> [ 113.755008] kvm: zapping shadow pages for mmio generation wraparound
Wow, this must have been there forever...
Paolo
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