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)
Change the ipte lock code to replace ACCESS_ONCE with READ_ONCE. Signed-off-by: Christian Borntraeger <[email protected]> --- arch/s390/kvm/gaccess.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c index 0f961a1..8f195fa 100644 --- a/arch/s390/kvm/gaccess.c +++ b/arch/s390/kvm/gaccess.c @@ -229,10 +229,10 @@ static void ipte_lock_simple(struct kvm_vcpu *vcpu) goto out; ic = &vcpu->kvm->arch.sca->ipte_control; do { - old = ACCESS_ONCE(*ic); + old = READ_ONCE(*ic); while (old.k) { cond_resched(); - old = ACCESS_ONCE(*ic); + old = READ_ONCE(*ic); } new = old; new.k = 1; @@ -251,7 +251,8 @@ static void ipte_unlock_simple(struct kvm_vcpu *vcpu) goto out; ic = &vcpu->kvm->arch.sca->ipte_control; do { - new = old = ACCESS_ONCE(*ic); + old = READ_ONCE(*ic); + new = old; new.k = 0; } while (cmpxchg(&ic->val, old.val, new.val) != old.val); wake_up(&vcpu->kvm->arch.ipte_wq); @@ -265,10 +266,10 @@ static void ipte_lock_siif(struct kvm_vcpu *vcpu) ic = &vcpu->kvm->arch.sca->ipte_control; do { - old = ACCESS_ONCE(*ic); + old = READ_ONCE(*ic); while (old.kg) { cond_resched(); - old = ACCESS_ONCE(*ic); + old = READ_ONCE(*ic); } new = old; new.k = 1; @@ -282,7 +283,8 @@ static void ipte_unlock_siif(struct kvm_vcpu *vcpu) ic = &vcpu->kvm->arch.sca->ipte_control; do { - new = old = ACCESS_ONCE(*ic); + old = READ_ONCE(*ic); + new = old; new.kh--; if (!new.kh) new.k = 0; -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
