[PATCH 4.0 46/55] KVM: s390: fix external call injection without sigp interpretation

Greg Kroah-Hartman
2015-07-08T08:00:12Z

From: David Hildenbrand <dahi@linux.vnet.ibm.com>

commit b938eacea0b6881f2116a061e6da3ec840e75137 upstream.

Commit ea5f49692575 ("KVM: s390: only one external call may be pending
at a time") introduced a bug on machines that don't have SIGP
interpretation facility installed.
The injection of an external call will now always fail with -EBUSY
(if none is already pending).

This leads to the following symptoms:
- An external call will be injected but with the wrong "src cpu id",
as this id will not be remembered.
- The target vcpu will not be woken up, therefore the guest will hang if
it cannot deal with unexpected failures of the SIGP EXTERNAL CALL
instruction.
- If an external call is already pending, -EBUSY will not be reported.

Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/s390/kvm/interrupt.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -1037,7 +1037,7 @@ static int __inject_extcall(struct kvm_v
if (sclp_has_sigpif())
return __inject_extcall_sigpif(vcpu, src_id);

- if (!test_and_set_bit(IRQ_PEND_EXT_EXTERNAL, &li->pending_irqs))
+ if (test_and_set_bit(IRQ_PEND_EXT_EXTERNAL, &li->pending_irqs))
return -EBUSY;
*extcall = irq->u.extcall;
atomic_set_mask(CPUSTAT_EXT_INT, li->cpuflags);