The diag 0x44 handler, which handles a directed yield, goes into a
a codepath that does a kvm_for_each_vcpu() and ultimately
deliverable_irqs().  The new check for kvm_s390_pv_cpu_is_protected()
contains an assertion that the vcpu->mutex is held, which isn't going
to be the case in this scenario.

The result is a plethora of these messages if the lock debugging
is enabled, and thus an implication that we have a problem.

  WARNING: CPU: 9 PID: 16167 at arch/s390/kvm/kvm-s390.h:239 deliverable_irqs+0x1c6/0x1d0 [kvm]
  ...snip...
  Call Trace:
   [<000003ff80429bf2>] deliverable_irqs+0x1ca/0x1d0 [kvm]
  ([<000003ff80429b34>] deliverable_irqs+0x10c/0x1d0 [kvm])
   [<000003ff8042ba82>] kvm_s390_vcpu_has_irq+0x2a/0xa8 [kvm]
   [<000003ff804101e2>] kvm_arch_dy_runnable+0x22/0x38 [kvm]
   [<000003ff80410284>] kvm_vcpu_on_spin+0x8c/0x1d0 [kvm]
   [<000003ff80436888>] kvm_s390_handle_diag+0x3b0/0x768 [kvm]
   [<000003ff80425af4>] kvm_handle_sie_intercept+0x1cc/0xcd0 [kvm]
   [<000003ff80422bb0>] __vcpu_run+0x7b8/0xfd0 [kvm]
   [<000003ff80423de6>] kvm_arch_vcpu_ioctl_run+0xee/0x3e0 [kvm]
   [<000003ff8040ccd8>] kvm_vcpu_ioctl+0x2c8/0x8d0 [kvm]
   [<00000001504ced06>] ksys_ioctl+0xae/0xe8
   [<00000001504cedaa>] __s390x_sys_ioctl+0x2a/0x38
   [<0000000150cb9034>] system_call+0xd8/0x2d8
  2 locks held by CPU 2/KVM/16167:
   #0: 00000001951980c0 (&vcpu->mutex){+.+.}, at: kvm_vcpu_ioctl+0x90/0x8d0 [kvm]
   #1: 000000019599c0f0 (&kvm->srcu){....}, at: __vcpu_run+0x4bc/0xfd0 [kvm]
  Last Breaking-Event-Address:
   [<000003ff80429b34>] deliverable_irqs+0x10c/0x1d0 [kvm]
  irq event stamp: 11967
  hardirqs last  enabled at (11975): [<00000001502992f2>] console_unlock+0x4ca/0x650
  hardirqs last disabled at (11982): [<0000000150298ee8>] console_unlock+0xc0/0x650
  softirqs last  enabled at (7940): [<0000000150cba6ca>] __do_softirq+0x422/0x4d8
  softirqs last disabled at (7929): [<00000001501cd688>] do_softirq_own_stack+0x70/0x80

Considering what's being done here, let's fix this by removing the
mutex assertion rather than acquiring the mutex for every other vcpu.

Fixes: 201ae986

 ("KVM: s390: protvirt: Implement interrupt injection")
Signed-off-by: Eric Farman <farman@linux.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Link: https://lore.kernel.org/r/20200415190353.63625-1-farman@linux.ibm.com


Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>