Patch "KVM: s390: fix external call injection without sigp interpretation" has been added to the 4.1-stable tree

This is a note to let you know that I've just added the patch titled

KVM: s390: fix external call injection without sigp interpretation

to the 4.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
kvm-s390-fix-external-call-injection-without-sigp-interpretation.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: David Hildenbrand <[email protected]>
Date: Thu, 30 Apr 2015 13:33:59 +0200
Subject: KVM: s390: fix external call injection without sigp interpretation

From: David Hildenbrand <[email protected]>

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.

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

@@ -1061,7 +1061,7 @@ 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);

Patches currently in stable-queue which might be from [email protected] are

queue-4.1/kvm-s390-fix-external-call-injection-without-sigp-interpretation.patch