KVM: s390: change ipte lock from barrier to READ_ONCE
Now that we have the READ_ONCE solution, we can change the ipte lock
from a barrier solution to READ_ONCE. The barrier and the explanation
of the bug was introduced in commit 1365039d0cb3 ("KVM: s390: Fix
ipte locking")
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
index 6dc0ad9..8f195fa 100644
--- a/arch/s390/kvm/gaccess.c
+++ b/arch/s390/kvm/gaccess.c
@@ -229,12 +229,10 @@
goto out;
ic = &vcpu->kvm->arch.sca->ipte_control;
do {
- old = *ic;
- barrier();
+ old = READ_ONCE(*ic);
while (old.k) {
cond_resched();
- old = *ic;
- barrier();
+ old = READ_ONCE(*ic);
}
new = old;
new.k = 1;
@@ -253,8 +251,7 @@
goto out;
ic = &vcpu->kvm->arch.sca->ipte_control;
do {
- old = *ic;
- barrier();
+ old = READ_ONCE(*ic);
new = old;
new.k = 0;
} while (cmpxchg(&ic->val, old.val, new.val) != old.val);
@@ -269,12 +266,10 @@
ic = &vcpu->kvm->arch.sca->ipte_control;
do {
- old = *ic;
- barrier();
+ old = READ_ONCE(*ic);
while (old.kg) {
cond_resched();
- old = *ic;
- barrier();
+ old = READ_ONCE(*ic);
}
new = old;
new.k = 1;
@@ -288,8 +283,7 @@
ic = &vcpu->kvm->arch.sca->ipte_control;
do {
- old = *ic;
- barrier();
+ old = READ_ONCE(*ic);
new = old;
new.kh--;
if (!new.kh)
