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authorChristian Borntraeger <borntraeger@de.ibm.com>2014-11-25 13:17:34 +0100
committerChristian Borntraeger <borntraeger@de.ibm.com>2014-12-18 09:54:41 +0100
commit5de72a2247ac05bde7c89039631b3d0c6186fafb (patch)
tree8ba7addcad7793f8e5ce0034c7f0a41a9039e222
parent488beef1440e845751365202faace2465840ea98 (diff)
s390/kvm: REPLACE barrier fixup with READ_ONCE
ACCESS_ONCE does not work reliably on non-scalar types. For example gcc 4.6 and 4.7 might remove the volatile tag for such accesses during the SRA (scalar replacement of aggregates) step (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145) Commit 1365039d0cb3 ("KVM: s390: Fix ipte locking") replace ACCESS_ONCE with barriers. Lets use READ_ONCE instead. Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
-rw-r--r--arch/s390/kvm/gaccess.c18
1 files changed, 6 insertions, 12 deletions
diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
index 6dc0ad9c7050..8f195fa904a1 100644
--- a/arch/s390/kvm/gaccess.c
+++ b/arch/s390/kvm/gaccess.c
@@ -229,12 +229,10 @@ static void ipte_lock_simple(struct kvm_vcpu *vcpu)
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 @@ static void ipte_unlock_simple(struct kvm_vcpu *vcpu)
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 @@ static void ipte_lock_siif(struct kvm_vcpu *vcpu)
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 @@ static void ipte_unlock_siif(struct kvm_vcpu *vcpu)
ic = &vcpu->kvm->arch.sca->ipte_control;
do {
- old = *ic;
- barrier();
+ old = READ_ONCE(*ic);
new = old;
new.kh--;
if (!new.kh)