libvhost-user: Fix some memtable remap cases

If a new setmemtable command comes in once the vhost threads are
running, it will remap the guests address space and the threads
will now be looking in the wrong place.

Fortunately we're running this command under lock, so we can
update the queue mappings so that threads will look in the new-right
place.

Note: This doesn't fix things that the threads might be doing
without a lock (e.g. a readv/writev!)  That's for another time.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

2 files changed, 28 insertions, 8 deletions

diff --git a/contrib/libvhost-user/libvhost-user.c b/contrib/libvhost-user/libvhost-user.c
index 63e41062a4..b89bf18501 100644
--- a/contrib/libvhost-user/libvhost-user.c
+++ b/contrib/libvhost-user/libvhost-user.c
@@ -565,6 +565,21 @@ vu_reset_device_exec(VuDev *dev, VhostUserMsg *vmsg)
 }
 
 static bool
+map_ring(VuDev *dev, VuVirtq *vq)
+{
+    vq->vring.desc = qva_to_va(dev, vq->vra.desc_user_addr);
+    vq->vring.used = qva_to_va(dev, vq->vra.used_user_addr);
+    vq->vring.avail = qva_to_va(dev, vq->vra.avail_user_addr);
+
+    DPRINT("Setting virtq addresses:\n");
+    DPRINT("    vring_desc  at %p\n", vq->vring.desc);
+    DPRINT("    vring_used  at %p\n", vq->vring.used);
+    DPRINT("    vring_avail at %p\n", vq->vring.avail);
+
+    return !(vq->vring.desc && vq->vring.used && vq->vring.avail);
+}
+
+static bool
 vu_set_mem_table_exec_postcopy(VuDev *dev, VhostUserMsg *vmsg)
 {
     int i;
@@ -767,6 +782,14 @@ vu_set_mem_table_exec(VuDev *dev, VhostUserMsg *vmsg)
         close(vmsg->fds[i]);
     }
 
+    for (i = 0; i < dev->max_queues; i++) {
+        if (dev->vq[i].vring.desc) {
+            if (map_ring(dev, &dev->vq[i])) {
+                vu_panic(dev, "remaping queue %d during setmemtable", i);
+            }
+        }
+    }
+
     return false;
 }
 
@@ -853,18 +876,12 @@ vu_set_vring_addr_exec(VuDev *dev, VhostUserMsg *vmsg)
     DPRINT("    avail_user_addr:  0x%016" PRIx64 "\n", vra->avail_user_addr);
     DPRINT("    log_guest_addr:   0x%016" PRIx64 "\n", vra->log_guest_addr);
 
+    vq->vra = *vra;
     vq->vring.flags = vra->flags;
-    vq->vring.desc = qva_to_va(dev, vra->desc_user_addr);
-    vq->vring.used = qva_to_va(dev, vra->used_user_addr);
-    vq->vring.avail = qva_to_va(dev, vra->avail_user_addr);
     vq->vring.log_guest_addr = vra->log_guest_addr;
 
-    DPRINT("Setting virtq addresses:\n");
-    DPRINT("    vring_desc  at %p\n", vq->vring.desc);
-    DPRINT("    vring_used  at %p\n", vq->vring.used);
-    DPRINT("    vring_avail at %p\n", vq->vring.avail);
 
-    if (!(vq->vring.desc && vq->vring.used && vq->vring.avail)) {
+    if (map_ring(dev, vq)) {
         vu_panic(dev, "Invalid vring_addr message");
         return false;
     }
diff --git a/contrib/libvhost-user/libvhost-user.h b/contrib/libvhost-user/libvhost-user.h
index 1844b6f8d4..5cb7708559 100644
--- a/contrib/libvhost-user/libvhost-user.h
+++ b/contrib/libvhost-user/libvhost-user.h
@@ -327,6 +327,9 @@ typedef struct VuVirtq {
     int err_fd;
     unsigned int enable;
     bool started;
+
+    /* Guest addresses of our ring */
+    struct vhost_vring_addr vra;
 } VuVirtq;
 
 enum VuWatchCondtion {