s390/ipl: Fix waiting for virtio processing

The guest side must not manipulate the index for the used buffers. Instead,
remember the state of the used buffer locally and wait until it has moved.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Acked-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

diff --git a/pc-bios/s390-ccw/virtio.c b/pc-bios/s390-ccw/virtio.c
index 49f2d291fcadb295e6b3cb1a9491e72cae7b7147..4d6e48fcbe0668790772d9468c3e752e6c0e5053 100644 (file)
--- a/pc-bios/s390-ccw/virtio.c
+++ b/pc-bios/s390-ccw/virtio.c
@@ -123,6 +123,7 @@ static void vring_init(struct vring *vr, unsigned int num, void *p,
     /* We're running with interrupts off anyways, so don't bother */
     vr->used->flags = VRING_USED_F_NO_NOTIFY;
     vr->used->idx = 0;
+    vr->used_idx = 0;
 
     debug_print_addr("init vr", vr);
 }
@@ -150,8 +151,6 @@ static void vring_send_buf(struct vring *vr, void *p, int len, int flags)
     if (!(flags & VRING_DESC_F_NEXT)) {
         vr->avail->idx++;
     }
-
-    vr->used->idx = vr->next_idx;
 }
 
 static u64 get_clock(void)
@@ -180,7 +179,8 @@ static int vring_wait_reply(struct vring *vr, int timeout)
     struct subchannel_id schid = vr->schid;
     int r = 0;
 
-    while (vr->used->idx == vr->next_idx) {
+    /* Wait until the used index has moved. */
+    while (vr->used->idx == vr->used_idx) {
         vring_notify(schid);
         if (timeout && (get_second() >= target_second)) {
             r = 1;
@@ -189,6 +189,7 @@ static int vring_wait_reply(struct vring *vr, int timeout)
         yield();
     }
 
+    vr->used_idx = vr->used->idx;
     vr->next_idx = 0;
     vr->desc[0].len = 0;
     vr->desc[0].flags = 0;

diff --git a/pc-bios/s390-ccw/virtio.h b/pc-bios/s390-ccw/virtio.h
index 86fdd579b451916754f0997bbd7e0e6f923a06ef..772a63f152cac824b1d0fa7f7895e73ab5be1914 100644 (file)
--- a/pc-bios/s390-ccw/virtio.h
+++ b/pc-bios/s390-ccw/virtio.h
@@ -115,6 +115,7 @@ struct vring_used {
 struct vring {
     unsigned int num;
     int next_idx;
+    int used_idx;
     struct vring_desc *desc;
     struct vring_avail *avail;
     struct vring_used *used;