KVM: S390: take a full byte as ext_param indicator

Currenty the ext_param field only distinguishes between "config change" and
"vring interrupt". We can do a lot more with it though, so let's enable a
full byte of possible values and constants to #defines while at it.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

2 files changed, 19 insertions, 6 deletions

diff --git a/arch/s390/include/asm/kvm_virtio.h b/arch/s390/include/asm/kvm_virtio.h
index acdfdff26611..3f5d100a42a2 100644
--- a/arch/s390/include/asm/kvm_virtio.h
+++ b/arch/s390/include/asm/kvm_virtio.h
@@ -54,4 +54,10 @@ struct kvm_vqconfig {
  * This is pagesize for historical reasons. */
 #define KVM_S390_VIRTIO_RING_ALIGN      4096
 
+
+/* These values are supposed to be in ext_params on an interrupt */
+#define VIRTIO_PARAM_MASK               0xff
+#define VIRTIO_PARAM_VRING_INTERRUPT    0x0
+#define VIRTIO_PARAM_CONFIG_CHANGED     0x1
+
 #endif
diff --git a/drivers/s390/kvm/kvm_virtio.c b/drivers/s390/kvm/kvm_virtio.c
index 4e298bc8949d..68cef4da15e8 100644
--- a/drivers/s390/kvm/kvm_virtio.c
+++ b/drivers/s390/kvm/kvm_virtio.c
@@ -334,7 +334,7 @@ static void kvm_extint_handler(u16 code)
 {
         struct virtqueue *vq;
         u16 subcode;
-        int config_changed;
+        u32 param;
 
         subcode = S390_lowcore.cpu_addr;
         if ((subcode & 0xff00) != VIRTIO_SUBCODE_64)
@@ -343,18 +343,25 @@ static void kvm_extint_handler(u16 code)
         /* The LSB might be overloaded, we have to mask it */
         vq = (struct virtqueue *)(S390_lowcore.ext_params2 & ~1UL);
 
-        /* We use the LSB of extparam, to decide, if this interrupt is a config
-         * change or a "standard" interrupt */
-        config_changed = S390_lowcore.ext_params & 1;
+        /* We use ext_params to decide what this interrupt means */
+        param = S390_lowcore.ext_params & VIRTIO_PARAM_MASK;
 
-        if (config_changed) {
+        switch (param) {
+        case VIRTIO_PARAM_CONFIG_CHANGED:
+        {
                 struct virtio_driver *drv;
                 drv = container_of(vq->vdev->dev.driver,
                                    struct virtio_driver, driver);
                 if (drv->config_changed)
                         drv->config_changed(vq->vdev);
-        } else
+
+                break;
+        }
+        case VIRTIO_PARAM_VRING_INTERRUPT:
+        default:
                 vring_interrupt(0, vq);
+                break;
+        }
 }
 
 /*