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* [PATCH v2] vfio/migration: Use BE byte order for device state wire packets
@ 2025-03-10 12:53 Maciej S. Szmigiero
  2025-03-10 13:14 ` Cédric Le Goater
  0 siblings, 1 reply; 2+ messages in thread
From: Maciej S. Szmigiero @ 2025-03-10 12:53 UTC (permalink / raw)
  To: Peter Xu, Fabiano Rosas
  Cc: Alex Williamson, Cédric Le Goater, Eric Blake,
	Markus Armbruster, Daniel P . Berrangé, Avihai Horon,
	Joao Martins, qemu-devel

From: "Maciej S. Szmigiero" <maciej.szmigiero@oracle.com>

Wire data commonly use BE byte order (including in the existing migration
protocol), use it also for for VFIO device state packets.

This will allow VFIO multifd device state transfer between hosts with
different endianness.
Although currently there is no such use case, it's good to have it now
for completeness.

Reviewed-by: Avihai Horon <avihaih@nvidia.com>
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
---
 hw/vfio/migration-multifd.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/hw/vfio/migration-multifd.c b/hw/vfio/migration-multifd.c
index a9d41b9f1cb1..e816461e1652 100644
--- a/hw/vfio/migration-multifd.c
+++ b/hw/vfio/migration-multifd.c
@@ -13,6 +13,7 @@
 #include "hw/vfio/vfio-common.h"
 #include "migration/misc.h"
 #include "qapi/error.h"
+#include "qemu/bswap.h"
 #include "qemu/error-report.h"
 #include "qemu/lockable.h"
 #include "qemu/main-loop.h"
@@ -208,12 +209,16 @@ bool vfio_multifd_load_state_buffer(void *opaque, char *data, size_t data_size,
         return false;
     }
 
+    packet->version = be32_to_cpu(packet->version);
     if (packet->version != VFIO_DEVICE_STATE_PACKET_VER_CURRENT) {
         error_setg(errp, "%s: packet has unknown version %" PRIu32,
                    vbasedev->name, packet->version);
         return false;
     }
 
+    packet->idx = be32_to_cpu(packet->idx);
+    packet->flags = be32_to_cpu(packet->flags);
+
     if (packet->idx == UINT32_MAX) {
         error_setg(errp, "%s: packet index is invalid", vbasedev->name);
         return false;
@@ -682,9 +687,9 @@ vfio_save_complete_precopy_thread_config_state(VFIODevice *vbasedev,
 
     packet_len = sizeof(*packet) + bioc->usage;
     packet = g_malloc0(packet_len);
-    packet->version = VFIO_DEVICE_STATE_PACKET_VER_CURRENT;
-    packet->idx = idx;
-    packet->flags = VFIO_DEVICE_STATE_CONFIG_STATE;
+    packet->version = cpu_to_be32(VFIO_DEVICE_STATE_PACKET_VER_CURRENT);
+    packet->idx = cpu_to_be32(idx);
+    packet->flags = cpu_to_be32(VFIO_DEVICE_STATE_CONFIG_STATE);
     memcpy(&packet->data, bioc->data, bioc->usage);
 
     if (!multifd_queue_device_state(idstr, instance_id,
@@ -734,7 +739,7 @@ vfio_multifd_save_complete_precopy_thread(SaveLiveCompletePrecopyThreadData *d,
     }
 
     packet = g_malloc0(sizeof(*packet) + migration->data_buffer_size);
-    packet->version = VFIO_DEVICE_STATE_PACKET_VER_CURRENT;
+    packet->version = cpu_to_be32(VFIO_DEVICE_STATE_PACKET_VER_CURRENT);
 
     for (idx = 0; ; idx++) {
         ssize_t data_size;
@@ -755,7 +760,7 @@ vfio_multifd_save_complete_precopy_thread(SaveLiveCompletePrecopyThreadData *d,
             break;
         }
 
-        packet->idx = idx;
+        packet->idx = cpu_to_be32(idx);
         packet_size = sizeof(*packet) + data_size;
 
         if (!multifd_queue_device_state(d->idstr, d->instance_id,


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