[v5,10/36] migration/multifd: Split packet into header and RAM data

Commit Message

Maciej S. Szmigiero Feb. 19, 2025, 8:33 p.m. UTC

From: "Maciej S. Szmigiero" <[e-mail]>

Read packet header first so in the future we will be able to
differentiate between a RAM multifd packet and a device state multifd
packet.

Since these two are of different size we can't read the packet body until
we know which packet type it is.

Reviewed-by: Fabiano Rosas <[e-mail]>
Reviewed-by: Peter Xu <[e-mail]>
Signed-off-by: Maciej S. Szmigiero <[e-mail]>
---
 migration/multifd.c | 55 ++++++++++++++++++++++++++++++++++++---------
 migration/multifd.h |  5 +++++
 2 files changed, 49 insertions(+), 11 deletions(-)

Patch

diff --git a/migration/multifd.c b/migration/multifd.c
index 215ad0414a79..3b47e63c2c4a 100644
--- a/migration/multifd.c
+++ b/migration/multifd.c
@@ -209,10 +209,10 @@  void multifd_send_fill_packet(MultiFDSendParams *p)
 
     memset(packet, 0, p->packet_len);
 
-    packet->magic = cpu_to_be32(MULTIFD_MAGIC);
-    packet->version = cpu_to_be32(MULTIFD_VERSION);
+    packet->hdr.magic = cpu_to_be32(MULTIFD_MAGIC);
+    packet->hdr.version = cpu_to_be32(MULTIFD_VERSION);
 
-    packet->flags = cpu_to_be32(p->flags);
+    packet->hdr.flags = cpu_to_be32(p->flags);
     packet->next_packet_size = cpu_to_be32(p->next_packet_size);
 
     packet_num = qatomic_fetch_inc(&multifd_send_state->packet_num);
@@ -228,12 +228,12 @@  void multifd_send_fill_packet(MultiFDSendParams *p)
                             p->flags, p->next_packet_size);
 }
 
-static int multifd_recv_unfill_packet(MultiFDRecvParams *p, Error **errp)
+static int multifd_recv_unfill_packet_header(MultiFDRecvParams *p,
+                                             const MultiFDPacketHdr_t *hdr,
+                                             Error **errp)
 {
-    const MultiFDPacket_t *packet = p->packet;
-    uint32_t magic = be32_to_cpu(packet->magic);
-    uint32_t version = be32_to_cpu(packet->version);
-    int ret = 0;
+    uint32_t magic = be32_to_cpu(hdr->magic);
+    uint32_t version = be32_to_cpu(hdr->version);
 
     if (magic != MULTIFD_MAGIC) {
         error_setg(errp, "multifd: received packet magic %x, expected %x",
@@ -247,7 +247,16 @@  static int multifd_recv_unfill_packet(MultiFDRecvParams *p, Error **errp)
         return -1;
     }
 
-    p->flags = be32_to_cpu(packet->flags);
+    p->flags = be32_to_cpu(hdr->flags);
+
+    return 0;
+}
+
+static int multifd_recv_unfill_packet(MultiFDRecvParams *p, Error **errp)
+{
+    const MultiFDPacket_t *packet = p->packet;
+    int ret = 0;
+
     p->next_packet_size = be32_to_cpu(packet->next_packet_size);
     p->packet_num = be64_to_cpu(packet->packet_num);
     p->packets_recved++;
@@ -1165,14 +1174,18 @@  static void *multifd_recv_thread(void *opaque)
     }
 
     while (true) {
+        MultiFDPacketHdr_t hdr;
         uint32_t flags = 0;
         bool has_data = false;
+        uint8_t *pkt_buf;
+        size_t pkt_len;
+
         p->normal_num = 0;
 
         if (use_packets) {
             struct iovec iov = {
-                .iov_base = (void *)p->packet,
-                .iov_len = p->packet_len
+                .iov_base = (void *)&hdr,
+                .iov_len = sizeof(hdr)
             };
 
             if (multifd_recv_should_exit()) {
@@ -1191,6 +1204,26 @@  static void *multifd_recv_thread(void *opaque)
                 break;
             }
 
+            ret = multifd_recv_unfill_packet_header(p, &hdr, &local_err);
+            if (ret) {
+                break;
+            }
+
+            pkt_buf = (uint8_t *)p->packet + sizeof(hdr);
+            pkt_len = p->packet_len - sizeof(hdr);
+
+            ret = qio_channel_read_all_eof(p->c, (char *)pkt_buf, pkt_len,
+                                           &local_err);
+            if (!ret) {
+                /* EOF */
+                error_setg(&local_err, "multifd: unexpected EOF after packet header");
+                break;
+            }
+
+            if (ret == -1) {
+                break;
+            }
+
             qemu_mutex_lock(&p->mutex);
             ret = multifd_recv_unfill_packet(p, &local_err);
             if (ret) {
diff --git a/migration/multifd.h b/migration/multifd.h
index cf408ff72140..f7156f66c0f6 100644
--- a/migration/multifd.h
+++ b/migration/multifd.h
@@ -69,6 +69,11 @@  typedef struct {
     uint32_t magic;
     uint32_t version;
     uint32_t flags;
+} __attribute__((packed)) MultiFDPacketHdr_t;
+
+typedef struct {
+    MultiFDPacketHdr_t hdr;
+
     /* maximum number of allocated pages */
     uint32_t pages_alloc;
     /* non zero pages */