[Qemu-devel] [RFC PATCH 4/7] virtio-fs: Add vhost-user slave commands for mapping

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

The daemon may request that fd's be mapped into the virtio-fs cache
visible to the guest.
These mappings are triggered by commands sent over the slave fd
from the daemon.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 contrib/libvhost-user/libvhost-user.h |  3 +++
 docs/interop/vhost-user.txt           | 35 +++++++++++++++++++++++++++
 hw/virtio/vhost-user-fs.c             | 20 +++++++++++++++
 hw/virtio/vhost-user.c                | 16 ++++++++++++
 include/hw/virtio/vhost-user-fs.h     | 24 ++++++++++++++++++
 5 files changed, 98 insertions(+)

diff --git a/contrib/libvhost-user/libvhost-user.h b/contrib/libvhost-user/libvhost-user.h
index 4aa55b4d2d..6cff0ff189 100644
--- a/contrib/libvhost-user/libvhost-user.h
+++ b/contrib/libvhost-user/libvhost-user.h
@@ -99,6 +99,9 @@ typedef enum VhostUserSlaveRequest {
     VHOST_USER_SLAVE_IOTLB_MSG = 1,
     VHOST_USER_SLAVE_CONFIG_CHANGE_MSG = 2,
     VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG = 3,
+    VHOST_USER_SLAVE_FS_MAP = 4,
+    VHOST_USER_SLAVE_FS_UNMAP = 5,
+    VHOST_USER_SLAVE_FS_SYNC = 6,
     VHOST_USER_SLAVE_MAX
 }  VhostUserSlaveRequest;
 
diff --git a/docs/interop/vhost-user.txt b/docs/interop/vhost-user.txt
index c2194711d9..29cdd74523 100644
--- a/docs/interop/vhost-user.txt
+++ b/docs/interop/vhost-user.txt
@@ -815,6 +815,41 @@ Slave message types
       This request should be sent only when VHOST_USER_PROTOCOL_F_HOST_NOTIFIER
       protocol feature has been successfully negotiated.
 
+ * VHOST_USER_SLAVE_FS_MAP
+
+      Id: 4
+      Equivalent ioctl: N/A
+      Slave payload: fd + n * (offset + address + len)
+      Master payload: N/A
+
+      Requests that the QEMU mmap the given fd into the virtio-fs cache;
+      multiple chunks can be mapped in one command.
+      A reply is generated indicating whether mapping succeeded.
+
+ * VHOST_USER_SLAVE_FS_UNMAP
+
+      Id: 5
+      Equivalent ioctl: N/A
+      Slave payload: n * (address + len)
+      Master payload: N/A
+
+      Requests that the QEMU un-mmap the given range in the virtio-fs cache;
+      multiple chunks can be unmapped in one command.
+      A reply is generated indicating whether unmapping succeeded.
+
+ * VHOST_USER_SLAVE_FS_SYNC
+
+      Id: 6
+      Equivalent ioctl: N/A
+      Slave payload: n * (address + len)
+      Master payload: N/A
+
+      Requests that the QEMU causes any changes to the virtio-fs cache to
+      be synchronised with the backing files.  Multiple chunks can be synced
+      in one command.
+      A reply is generated indicating whether syncing succeeded.
+      [Semantic details TBD]
+
 VHOST_USER_PROTOCOL_F_REPLY_ACK:
 -------------------------------
 The original vhost-user specification only demands replies for certain
diff --git a/hw/virtio/vhost-user-fs.c b/hw/virtio/vhost-user-fs.c
index 14ee922661..da70d9cd2c 100644
--- a/hw/virtio/vhost-user-fs.c
+++ b/hw/virtio/vhost-user-fs.c
@@ -21,6 +21,26 @@
 #include "hw/virtio/vhost-user-fs.h"
 #include "monitor/monitor.h"
 
+int vhost_user_fs_slave_map(struct vhost_dev *dev, VhostUserFSSlaveMsg *sm,
+                            int fd)
+{
+    /* TODO */
+    return -1;
+}
+
+int vhost_user_fs_slave_unmap(struct vhost_dev *dev, VhostUserFSSlaveMsg *sm)
+{
+    /* TODO */
+    return -1;
+}
+
+int vhost_user_fs_slave_sync(struct vhost_dev *dev, VhostUserFSSlaveMsg *sm)
+{
+    /* TODO */
+    return -1;
+}
+
+
 static void vuf_get_config(VirtIODevice *vdev, uint8_t *config)
 {
     VHostUserFS *fs = VHOST_USER_FS(vdev);
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index e09bed0e4a..beb028c7e2 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -12,6 +12,7 @@
 #include "qapi/error.h"
 #include "hw/virtio/vhost.h"
 #include "hw/virtio/vhost-user.h"
+#include "hw/virtio/vhost-user-fs.h"
 #include "hw/virtio/vhost-backend.h"
 #include "hw/virtio/virtio.h"
 #include "hw/virtio/virtio-net.h"
@@ -97,6 +98,9 @@ typedef enum VhostUserSlaveRequest {
     VHOST_USER_SLAVE_IOTLB_MSG = 1,
     VHOST_USER_SLAVE_CONFIG_CHANGE_MSG = 2,
     VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG = 3,
+    VHOST_USER_SLAVE_FS_MAP = 4,
+    VHOST_USER_SLAVE_FS_UNMAP = 5,
+    VHOST_USER_SLAVE_FS_SYNC = 6,
     VHOST_USER_SLAVE_MAX
 }  VhostUserSlaveRequest;
 
@@ -169,6 +173,7 @@ typedef union {
         VhostUserConfig config;
         VhostUserCryptoSession session;
         VhostUserVringArea area;
+        VhostUserFSSlaveMsg fs;
 } VhostUserPayload;
 
 typedef struct VhostUserMsg {
@@ -1010,6 +1015,17 @@ static void slave_read(void *opaque)
         ret = vhost_user_slave_handle_vring_host_notifier(dev, &payload.area,
                                                           fd[0]);
         break;
+#ifdef CONFIG_VHOST_USER_FS
+    case VHOST_USER_SLAVE_FS_MAP:
+        ret = vhost_user_fs_slave_map(dev, &payload.fs, fd[0]);
+        break;
+    case VHOST_USER_SLAVE_FS_UNMAP:
+        ret = vhost_user_fs_slave_unmap(dev, &payload.fs);
+        break;
+    case VHOST_USER_SLAVE_FS_SYNC:
+        ret = vhost_user_fs_slave_sync(dev, &payload.fs);
+        break;
+#endif
     default:
         error_report("Received unexpected msg type.");
         ret = -EINVAL;
diff --git a/include/hw/virtio/vhost-user-fs.h b/include/hw/virtio/vhost-user-fs.h
index be153e1c7a..9989bcd9e7 100644
--- a/include/hw/virtio/vhost-user-fs.h
+++ b/include/hw/virtio/vhost-user-fs.h
@@ -23,6 +23,24 @@
 #define VHOST_USER_FS(obj) \
         OBJECT_CHECK(VHostUserFS, (obj), TYPE_VHOST_USER_FS)
 
+/* Structures carried over the slave channel back to QEMU */
+#define VHOST_USER_FS_SLAVE_ENTRIES 8
+
+/* For the flags field of VhostUserFSSlaveMsg */
+#define VHOST_USER_FS_FLAG_MAP_R (1ull << 0)
+#define VHOST_USER_FS_FLAG_MAP_W (1ull << 1)
+
+typedef struct {
+    /* Offsets within the file being mapped */
+    uint64_t fd_offset[VHOST_USER_FS_SLAVE_ENTRIES];
+    /* Offsets within the cache */
+    uint64_t c_offset[VHOST_USER_FS_SLAVE_ENTRIES];
+    /* Lengths of sections */
+    uint64_t len[VHOST_USER_FS_SLAVE_ENTRIES];
+    /* Flags, from VHOST_USER_FS_FLAG_* */
+    uint64_t flags[VHOST_USER_FS_SLAVE_ENTRIES];
+} VhostUserFSSlaveMsg;
+
 typedef struct {
     CharBackend chardev;
     char *tag;
@@ -44,4 +62,10 @@ typedef struct {
     MemoryRegion cache;
 } VHostUserFS;
 
+/* Callbacks from the vhost-user code for slave commands */
+int vhost_user_fs_slave_map(struct vhost_dev *dev, VhostUserFSSlaveMsg *sm,
+                            int fd);
+int vhost_user_fs_slave_unmap(struct vhost_dev *dev, VhostUserFSSlaveMsg *sm);
+int vhost_user_fs_slave_sync(struct vhost_dev *dev, VhostUserFSSlaveMsg *sm);
+
 #endif /* _QEMU_VHOST_USER_FS_H */
-- 
2.19.2