[VirtIO] Define and use VQ_ADD_BUFFER_SUCCESS

Define VQ_ADD_BUFFER_SUCCESS in VirtIO\virtio_ring.h
Update return code on success in virtqueue_add_buf() routines to use
VQ_ADD_BUFFER_SUCCESS. These are:
virtqueue_add_buf_split() in VirtIO\VirtIORing.c
virtqueue_add_buf_packed() in VirtIO\VirtIORing-Packed.c

Signed-off-by: benyamin-codez <115509179+benyamin-codez@users.noreply.github.com>

VirtIO/VirtIORing-Packed.c

@@ -288,7 +288,7 @@ static int virtqueue_add_buf_packed(
         DPrintf(5, "Added buffer head @%i+%d to Q%d\n", head, descs_used, vq->vq.index);
     }
 
-    return 0;
+    return VQ_ADD_BUFFER_SUCCESS;
 }
 
 static void detach_buf_packed(struct virtqueue_packed *vq, unsigned int id)

VirtIO/VirtIORing.c

@@ -296,7 +296,7 @@ static int virtqueue_add_buf_split(
     vring->avail->idx = ++vq->master_vring_avail.idx;
     vq->num_added_since_kick++;
 
-    return 0;
+    return VQ_ADD_BUFFER_SUCCESS;
 }
 
 /* Gets the opaque pointer associated with a returned buffer, or NULL if no buffer is available */

VirtIO/virtio_ring.h

@@ -44,6 +44,8 @@
 * at the end of the used ring. Guest should ignore the used->flags field. */
 #define VIRTIO_RING_F_EVENT_IDX		29
 
+#define VQ_ADD_BUFFER_SUCCESS 0
+
 void vring_transport_features(VirtIODevice *vdev, u64 *features);
 unsigned long vring_size(unsigned int num, unsigned long align, bool packed);
 

vioscsi/helper.h

@@ -40,6 +40,7 @@
 
 #include "osdep.h"
 #include "virtio_pci.h"
+#include "virtio_ring.h"
 #include "vioscsi.h"
 
 #define CHECKBIT(value, nbit) virtio_is_feature_enabled(value, nbit)
@@ -49,8 +50,6 @@
 #define CACHE_LINE_SIZE 64
 #define ROUND_TO_CACHE_LINES(Size)  (((ULONG_PTR)(Size) + CACHE_LINE_SIZE - 1) & ~(CACHE_LINE_SIZE - 1))
 
-#define VQ_ADD_BUFFER_SUCCESS 0
-
 #include <srbhelper.h>
 
 // Note: SrbGetCdbLength is defined in srbhelper.h