Reacquire kvm->srcu in vcpu_run() before returning to the caller if srcu
was dropped to handle pending work. If the task receives a signal, KVM
will exit without reacquiring kvm->srcu, resulting in an unbalanced
unlock kvm_arch_vcpu_ioctl_run(), and eventually hung tasks.
=====================================
WARNING: bad unlock balance detected!
5.17.0-rc3+ #749 Not tainted
-------------------------------------
CPU 0/KVM/1803 is trying to release lock (&kvm->srcu) at:
[<ffffffff81042a19>] kvm_arch_vcpu_ioctl_run+0x669/0x1f60
but there are no more locks to release!
other info that might help us debug this:
1 lock held by CPU 0/KVM/1803:
#0: ffff88810489c0b0 (&vcpu->mutex){....}-{3:3}, at: kvm_vcpu_ioctl+0x77/0x690
stack backtrace:
CPU: 7 PID: 1803 Comm: CPU 0/KVM Not tainted 5.17.0-rc3+ #749
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
Call Trace:
<TASK>
dump_stack_lvl+0x34/0x44
lock_release+0x1b4/0x240
kvm_arch_vcpu_ioctl_run+0x680/0x1f60
kvm_vcpu_ioctl+0x279/0x690
__x64_sys_ioctl+0x83/0xb0
do_syscall_64+0x3b/0xc0
entry_SYSCALL_64_after_hwframe+0x44/0xae
</TASK>
INFO: task stable:2347 blocked for more than 120 seconds.
Not tainted 5.17.0-rc3+ #749
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:stable state:D stack: 0 pid: 2347 ppid: 2340 flags:0x00000000
Call Trace:
<TASK>
__schedule+0x328/0xa00
schedule+0x44/0xb0
schedule_timeout+0x26f/0x300
wait_for_completion+0x84/0xe0
__synchronize_srcu.part.0+0x7a/0xa0
kvm_swap_active_memslots+0x141/0x180
kvm_set_memslot+0x2f9/0x470
kvm_set_memory_region+0x29/0x40
kvm_vm_ioctl+0x2c3/0xd70
__x64_sys_ioctl+0x83/0xb0
do_syscall_64+0x3b/0xc0
entry_SYSCALL_64_after_hwframe+0x44/0xae
</TASK>
INFO: lockdep is turned off.
Fixes: 5d8d2bfc5e65 ("KVM: x86: pull kvm->srcu read-side to kvm_arch_vcpu_ioctl_run")
Cc: Like Xu <like.xu.linux@xxxxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/x86/kvm/x86.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e55de9b48d1a..6de4d810f5b2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10281,9 +10281,10 @@ static int vcpu_run(struct kvm_vcpu *vcpu)
if (__xfer_to_guest_mode_work_pending()) {
srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
r = xfer_to_guest_mode_handle_work(vcpu);
+ vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
+
if (r)
return r;
- vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
}
}
base-commit: 991f988b43c5ee82ef681907bfe979bee93a55c2
--
2.35.1.574.g5d30c73bfb-goog
