3.18-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit 5de72a2247ac05bde7c89039631b3d0c6186fafb ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/kvm/gaccess.c | 18 ++++++------------ 1 file 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)