[PATCH RFC 03/15] vhost: Return number of free memslots

[David Hildenbrand <david@redhat.com>]

Let's return the number of free slots instead of only checking if there
is a free slot. Required to support memory devices that consume multiple
memslots.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 hw/mem/memory-device.c    | 2 +-
 hw/virtio/vhost-stub.c    | 2 +-
 hw/virtio/vhost.c         | 4 ++--
 include/hw/virtio/vhost.h | 2 +-
 4 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/hw/mem/memory-device.c b/hw/mem/memory-device.c
index 9045ead33e..7f76a09e57 100644
--- a/hw/mem/memory-device.c
+++ b/hw/mem/memory-device.c
@@ -77,7 +77,7 @@ static void memory_device_check_addable(MachineState *ms, uint64_t size,
         error_setg(errp, "hypervisor has no free memory slots left");
         return;
     }
-    if (!vhost_has_free_slot()) {
+    if (!vhost_get_free_memslots()) {
         error_setg(errp, "a used vhost backend has no free memory slots left");
         return;
     }
diff --git a/hw/virtio/vhost-stub.c b/hw/virtio/vhost-stub.c
index c175148fce..fe111e5e45 100644
--- a/hw/virtio/vhost-stub.c
+++ b/hw/virtio/vhost-stub.c
@@ -2,7 +2,7 @@
 #include "hw/virtio/vhost.h"
 #include "hw/virtio/vhost-user.h"
 
-bool vhost_has_free_slot(void)
+unsigned int vhost_get_free_memslots(void)
 {
     return true;
 }
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 437347ad01..2707972870 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -48,7 +48,7 @@ static unsigned int used_memslots;
 static QLIST_HEAD(, vhost_dev) vhost_devices =
     QLIST_HEAD_INITIALIZER(vhost_devices);
 
-bool vhost_has_free_slot(void)
+unsigned int vhost_get_free_memslots(void)
 {
     unsigned int slots_limit = ~0U;
     struct vhost_dev *hdev;
@@ -57,7 +57,7 @@ bool vhost_has_free_slot(void)
         unsigned int r = hdev->vhost_ops->vhost_backend_memslots_limit(hdev);
         slots_limit = MIN(slots_limit, r);
     }
-    return slots_limit > used_memslots;
+    return slots_limit - used_memslots;
 }
 
 static void vhost_dev_sync_region(struct vhost_dev *dev,
diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
index 1a9fc65089..1613af8855 100644
--- a/include/hw/virtio/vhost.h
+++ b/include/hw/virtio/vhost.h
@@ -128,7 +128,7 @@ uint64_t vhost_get_features(struct vhost_dev *hdev, const int *feature_bits,
                             uint64_t features);
 void vhost_ack_features(struct vhost_dev *hdev, const int *feature_bits,
                         uint64_t features);
-bool vhost_has_free_slot(void);
+unsigned int vhost_get_free_memslots(void);
 
 int vhost_net_set_backend(struct vhost_dev *hdev,
                           struct vhost_vring_file *file);
-- 
2.31.1