vfio-user: implement message receive infrastructure

Add the basic implementation for receiving vfio-user messages from the
control socket.

Originally-by: John Johnson <john.g.johnson@oracle.com>
Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>
Signed-off-by: John Levon <john.levon@nutanix.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20250625193012.2316242-4-john.levon@nutanix.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>

1 files changed, 53 insertions, 0 deletions

diff --git a/hw/vfio-user/protocol.h b/hw/vfio-user/protocol.h
new file mode 100644
index 0000000000..4ddfb5f222
--- /dev/null
+++ b/hw/vfio-user/protocol.h
@@ -0,0 +1,53 @@
+#ifndef VFIO_USER_PROTOCOL_H
+#define VFIO_USER_PROTOCOL_H
+
+/*
+ * vfio protocol over a UNIX socket.
+ *
+ * Copyright © 2018, 2021 Oracle and/or its affiliates.
+ *
+ * Each message has a standard header that describes the command
+ * being sent, which is almost always a VFIO ioctl().
+ *
+ * The header may be followed by command-specific data, such as the
+ * region and offset info for read and write commands.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+typedef struct {
+    uint16_t id;
+    uint16_t command;
+    uint32_t size;
+    uint32_t flags;
+    uint32_t error_reply;
+} VFIOUserHdr;
+
+/* VFIOUserHdr commands */
+enum vfio_user_command {
+    VFIO_USER_VERSION                   = 1,
+    VFIO_USER_DMA_MAP                   = 2,
+    VFIO_USER_DMA_UNMAP                 = 3,
+    VFIO_USER_DEVICE_GET_INFO           = 4,
+    VFIO_USER_DEVICE_GET_REGION_INFO    = 5,
+    VFIO_USER_DEVICE_GET_REGION_IO_FDS  = 6,
+    VFIO_USER_DEVICE_GET_IRQ_INFO       = 7,
+    VFIO_USER_DEVICE_SET_IRQS           = 8,
+    VFIO_USER_REGION_READ               = 9,
+    VFIO_USER_REGION_WRITE              = 10,
+    VFIO_USER_DMA_READ                  = 11,
+    VFIO_USER_DMA_WRITE                 = 12,
+    VFIO_USER_DEVICE_RESET              = 13,
+    VFIO_USER_DIRTY_PAGES               = 14,
+    VFIO_USER_MAX,
+};
+
+/* VFIOUserHdr flags */
+#define VFIO_USER_REQUEST       0x0
+#define VFIO_USER_REPLY         0x1
+#define VFIO_USER_TYPE          0xF
+
+#define VFIO_USER_NO_REPLY      0x10
+#define VFIO_USER_ERROR         0x20
+
+#endif /* VFIO_USER_PROTOCOL_H */