[Qemu-devel] [PATCH v2 11/45] ivshmem: increase_dynamic_storage() improvements

[Marc-André Lureau]

From: Marc-André Lureau <address@hidden>

- rename the function resize_peers() to better reflect the content

- limit the maximum number of peers to IVSHMEM_MAX_PEERS as MAXUINT16,
which is more realistic and also better reflects the limit of the
doorbell register.

- change the argument to be the size, not the 0-index max value

- immediately allocate the eventfds instead of lazily

Signed-off-by: Marc-André Lureau <address@hidden>
---
 hw/misc/ivshmem.c | 43 ++++++++++++++++---------------------------
 1 file changed, 16 insertions(+), 27 deletions(-)

diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c
index 7ba93c0..66f9c0b 100644
--- a/hw/misc/ivshmem.c
+++ b/hw/misc/ivshmem.c
@@ -34,6 +34,7 @@
 #define PCI_VENDOR_ID_IVSHMEM   PCI_VENDOR_ID_REDHAT_QUMRANET
 #define PCI_DEVICE_ID_IVSHMEM   0x1110
 
+#define IVSHMEM_MAX_PEERS G_MAXUINT16
 #define IVSHMEM_IOEVENTFD   0
 #define IVSHMEM_MSI     1
 
@@ -416,31 +417,28 @@ static void close_guest_eventfds(IVShmemState *s, int 
posn)
 
 /* this function increase the dynamic storage need to store data about other
  * guests */
-static int increase_dynamic_storage(IVShmemState *s, int new_min_size)
+static int resize_peers(IVShmemState *s, int new_min_size)
 {
 
-    int j, old_nb_alloc;
+    int j, old_size;
 
-    /* check for integer overflow */
-    if (new_min_size >= INT_MAX / sizeof(Peer) - 1 || new_min_size <= 0) {
+    /* limit number of max peers */
+    if (new_min_size <= 0 || new_min_size > IVSHMEM_MAX_PEERS) {
         return -1;
     }
-
-    old_nb_alloc = s->nb_peers;
-
-    if (new_min_size >= s->nb_peers) {
-        /* +1 because #new_min_size is used as last array index */
-        s->nb_peers = new_min_size + 1;
-    } else {
+    if (new_min_size <= s->nb_peers) {
         return 0;
     }
 
+    old_size = s->nb_peers;
+    s->nb_peers = new_min_size;
+
     IVSHMEM_DPRINTF("bumping storage to %d guests\n", s->nb_peers);
+
     s->peers = g_realloc(s->peers, s->nb_peers * sizeof(Peer));
 
-    /* zero out new pointers */
-    for (j = old_nb_alloc; j < s->nb_peers; j++) {
-        s->peers[j].eventfds = NULL;
+    for (j = old_size; j < s->nb_peers; j++) {
+        s->peers[j].eventfds = g_new(EventNotifier, s->vectors);
         s->peers[j].nb_eventfds = 0;
     }
 
@@ -507,8 +505,8 @@ static void ivshmem_read(void *opaque, const uint8_t *buf, 
int size)
 
     /* make sure we have enough space for this guest */
     if (incoming_posn >= s->nb_peers) {
-        if (increase_dynamic_storage(s, incoming_posn) < 0) {
-            error_report("increase_dynamic_storage() failed");
+        if (resize_peers(s, incoming_posn + 1) < 0) {
+            error_report("failed to resize peers array");
             if (incoming_fd != -1) {
                 close(incoming_fd);
             }
@@ -518,8 +516,7 @@ static void ivshmem_read(void *opaque, const uint8_t *buf, 
int size)
 
     if (incoming_fd == -1) {
         /* if posn is positive and unseen before then this is our posn*/
-        if ((incoming_posn >= 0) &&
-                            (s->peers[incoming_posn].eventfds == NULL)) {
+        if (incoming_posn >= 0 && s->vm_id == -1) {
             /* receive our posn */
             s->vm_id = incoming_posn;
             return;
@@ -570,11 +567,6 @@ static void ivshmem_read(void *opaque, const uint8_t *buf, 
int size)
      * guests for each VM */
     guest_max_eventfd = s->peers[incoming_posn].nb_eventfds;
 
-    if (guest_max_eventfd == 0) {
-        /* one eventfd per MSI vector */
-        s->peers[incoming_posn].eventfds = g_new(EventNotifier, s->vectors);
-    }
-
     /* this is an eventfd for a particular guest VM */
     IVSHMEM_DPRINTF("eventfds[%ld][%d] = %d\n", incoming_posn,
                     guest_max_eventfd, incoming_fd);
@@ -811,12 +803,9 @@ static void pci_ivshmem_realize(PCIDevice *dev, Error 
**errp)
         }
 
         /* we allocate enough space for 16 guests and grow as needed */
-        s->nb_peers = 16;
+        resize_peers(s, 16);
         s->vm_id = -1;
 
-        /* allocate/initialize space for interrupt handling */
-        s->peers = g_malloc0(s->nb_peers * sizeof(Peer));
-
         pci_register_bar(dev, 2, attr, &s->bar);
 
         s->eventfd_chr = g_malloc0(s->vectors * sizeof(CharDriverState *));
-- 
2.4.3