Patch "KVM: s390: no need to hold the kvm->mutex for floating interrupts" has been added to the 3.19-stable tree

[<gregkh@linuxfoundation.org>]

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

    KVM: s390: no need to hold the kvm->mutex for floating interrupts

to the 3.19-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-no-need-to-hold-the-kvm-mutex-for-floating-interrupts.patch
and it can be found in the queue-3.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 69a8d456263849152826542c7cb0a164b90e68a8 Mon Sep 17 00:00:00 2001
From: Christian Borntraeger <borntraeger@de.ibm.com>
Date: Wed, 17 Dec 2014 10:36:04 +0100
Subject: KVM: s390: no need to hold the kvm->mutex for floating interrupts

From: Christian Borntraeger <borntraeger@de.ibm.com>

commit 69a8d456263849152826542c7cb0a164b90e68a8 upstream.

The kvm mutex was (probably) used to protect against cpu hotplug.
The current code no longer needs to protect against that, as we only
rely on CPU data structures that are guaranteed to be available
if we can access the CPU. (e.g. vcpu_create will put the cpu
in the array AFTER the cpu is ready).

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/s390/kvm/interrupt.c |    8 --------
 1 file changed, 8 deletions(-)

--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -1131,7 +1131,6 @@ struct kvm_s390_interrupt_info *kvm_s390
 
 	if ((!schid && !cr6) || (schid && cr6))
 		return NULL;
-	mutex_lock(&kvm->lock);
 	fi = &kvm->arch.float_int;
 	spin_lock(&fi->lock);
 	inti = NULL;
@@ -1159,7 +1158,6 @@ struct kvm_s390_interrupt_info *kvm_s390
 	if (list_empty(&fi->list))
 		atomic_set(&fi->active, 0);
 	spin_unlock(&fi->lock);
-	mutex_unlock(&kvm->lock);
 	return inti;
 }
 
@@ -1172,7 +1170,6 @@ static int __inject_vm(struct kvm *kvm,
 	int sigcpu;
 	int rc = 0;
 
-	mutex_lock(&kvm->lock);
 	fi = &kvm->arch.float_int;
 	spin_lock(&fi->lock);
 	if (fi->irq_count >= KVM_S390_MAX_FLOAT_IRQS) {
@@ -1225,7 +1222,6 @@ static int __inject_vm(struct kvm *kvm,
 	kvm_s390_vcpu_wakeup(kvm_get_vcpu(kvm, sigcpu));
 unlock_fi:
 	spin_unlock(&fi->lock);
-	mutex_unlock(&kvm->lock);
 	return rc;
 }
 
@@ -1379,7 +1375,6 @@ void kvm_s390_clear_float_irqs(struct kv
 	struct kvm_s390_float_interrupt *fi;
 	struct kvm_s390_interrupt_info	*n, *inti = NULL;
 
-	mutex_lock(&kvm->lock);
 	fi = &kvm->arch.float_int;
 	spin_lock(&fi->lock);
 	list_for_each_entry_safe(inti, n, &fi->list, list) {
@@ -1389,7 +1384,6 @@ void kvm_s390_clear_float_irqs(struct kv
 	fi->irq_count = 0;
 	atomic_set(&fi->active, 0);
 	spin_unlock(&fi->lock);
-	mutex_unlock(&kvm->lock);
 }
 
 static inline int copy_irq_to_user(struct kvm_s390_interrupt_info *inti,
@@ -1429,7 +1423,6 @@ static int get_all_floating_irqs(struct
 	int ret = 0;
 	int n = 0;
 
-	mutex_lock(&kvm->lock);
 	fi = &kvm->arch.float_int;
 	spin_lock(&fi->lock);
 
@@ -1448,7 +1441,6 @@ static int get_all_floating_irqs(struct
 	}
 
 	spin_unlock(&fi->lock);
-	mutex_unlock(&kvm->lock);
 
 	return ret < 0 ? ret : n;
 }


Patches currently in stable-queue which might be from borntraeger@de.ibm.com are

queue-3.19/kvm-s390-zero-out-current-vmdb-of-stsi-before-including-level3-data.patch
queue-3.19/kvm-s390-reinjection-of-irqs-can-fail-in-the-tpi-handler.patch
queue-3.19/kvm-s390-fix-get_all_floating_irqs.patch
queue-3.19/kvm-s390-no-need-to-hold-the-kvm-mutex-for-floating-interrupts.patch
queue-3.19/kvm-s390-fix-handling-of-write-errors-in-the-tpi-handler.patch