On Wed, Dec 03, 2014 at 11:30:20PM +0100, Christian Borntraeger wrote: > 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]>
Acked-by: Paul E. McKenney <[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/
