releases/4.0.8/kvm-s390-fix-external-call-injection-without-sigp-interpretation.patch

   1 From b938eacea0b6881f2116a061e6da3ec840e75137 Mon Sep 17 00:00:00 2001
   2 From: David Hildenbrand <dahi@linux.vnet.ibm.com>
   3 Date: Thu, 30 Apr 2015 13:33:59 +0200
   4 Subject: KVM: s390: fix external call injection without sigp interpretation
   5
   6 From: David Hildenbrand <dahi@linux.vnet.ibm.com>
   7
   8 commit b938eacea0b6881f2116a061e6da3ec840e75137 upstream.
   9
  10 Commit ea5f49692575 ("KVM: s390: only one external call may be pending
  11 at a time") introduced a bug on machines that don't have SIGP
  12 interpretation facility installed.
  13 The injection of an external call will now always fail with -EBUSY
  14 (if none is already pending).
  15
  16 This leads to the following symptoms:
  17 - An external call will be injected but with the wrong "src cpu id",
  18   as this id will not be remembered.
  19 - The target vcpu will not be woken up, therefore the guest will hang if
  20   it cannot deal with unexpected failures of the SIGP EXTERNAL CALL
  21   instruction.
  22 - If an external call is already pending, -EBUSY will not be reported.
  23
  24 Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
  25 Reviewed-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
  26 Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
  27 Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
  28 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  29
  30 ---
  31  arch/s390/kvm/interrupt.c |    2 +-
  32  1 file changed, 1 insertion(+), 1 deletion(-)
  33
  34 --- a/arch/s390/kvm/interrupt.c
  35 +++ b/arch/s390/kvm/interrupt.c
  36 @@ -1037,7 +1037,7 @@ static int __inject_extcall(struct kvm_v
  37         if (sclp_has_sigpif())
  38                 return __inject_extcall_sigpif(vcpu, src_id);
  39
  40 -       if (!test_and_set_bit(IRQ_PEND_EXT_EXTERNAL, &li->pending_irqs))
  41 +       if (test_and_set_bit(IRQ_PEND_EXT_EXTERNAL, &li->pending_irqs))
  42                 return -EBUSY;
  43         *extcall = irq->u.extcall;
  44         atomic_set_mask(CPUSTAT_EXT_INT, li->cpuflags);