vhost-user: don't merge regions with different fds

vhost currently merges regions with contiguious virtual and physical
addresses.  This breaks for vhost-user since that also needs fds to
match.

Add a vhost_ops entry to compare the fds for vhost-user only.

Cc: qemu-stable@nongnu.org
Cc: Victor Kaplansky <victork@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 7fde1370e0..7ed3dd9a13 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -611,6 +611,25 @@ static int vhost_user_migration_done(struct vhost_dev *dev, char* mac_addr)
     return -1;
 }
 
+static bool vhost_user_can_merge(struct vhost_dev *dev,
+                                 uint64_t start1, uint64_t size1,
+                                 uint64_t start2, uint64_t size2)
+{
+    ram_addr_t ram_addr;
+    int mfd, rfd;
+    MemoryRegion *mr;
+
+    mr = qemu_ram_addr_from_host((void *)(uintptr_t)start1, &ram_addr);
+    assert(mr);
+    mfd = qemu_get_ram_fd(ram_addr);
+
+    mr = qemu_ram_addr_from_host((void *)(uintptr_t)start2, &ram_addr);
+    assert(mr);
+    rfd = qemu_get_ram_fd(ram_addr);
+
+    return mfd == rfd;
+}
+
 const VhostOps user_ops = {
         .backend_type = VHOST_BACKEND_TYPE_USER,
         .vhost_backend_init = vhost_user_init,
@@ -633,4 +652,5 @@ const VhostOps user_ops = {
         .vhost_set_vring_enable = vhost_user_set_vring_enable,
         .vhost_requires_shm_log = vhost_user_requires_shm_log,
         .vhost_migration_done = vhost_user_migration_done,
+        .vhost_backend_can_merge = vhost_user_can_merge,
 };