Old kernels did not check for zero in the irq_state.flags field and old
QEMUs did not zero the flag field when calling KVM_S390_*_IRQ_STATE.
Let's add a comment and dummy code to prevent future usage of flags
and pad.
Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
---
arch/s390/kvm/kvm-s390.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 6a5e02f..1baa393 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -3834,6 +3834,16 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
r = -EINVAL;
break;
}
+ if (irq_state.flags) {
+ /*
+ * This is a placeholder to make sure that nobody uses
+ * flags and pad. Old kernels did not check for zero
+ * and old QEMUs did not zero the flag field.
+ * That means that we cannot use the flags field for
+ * any possible extension.
+ */
+ irq_state.flags = 0;
+ }
r = kvm_s390_set_irq_state(vcpu,
(void __user *) irq_state.buf,
irq_state.len);
@@ -3849,6 +3859,10 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
r = -EINVAL;
break;
}
+ if (irq_state.flags) {
+ /* see above */
+ irq_state.flags = 0;
+ }
r = kvm_s390_get_irq_state(vcpu,
(__u8 __user *) irq_state.buf,
irq_state.len);
--
2.9.4
