[Qemu-devel] [PATCH v4] tests/vhost-user-bridge: implement logging of dirty pages

[Victor Kaplansky]

During migration devices continue writing to the guest's memory.
The writes has to be reported to QEMU. This change implements
minimal support in vhost-user-bridge required for successful
migration of a guest with virtio-net device.

Signed-off-by: Victor Kaplansky <address@hidden>
---
v4:
    - implement set_vring_enable()
    - stop the device on vubr_get_vring_base_exec() and
      start on setting kick_fd as a work-around to QEMU bug
      enabling vrings too early.
v3:
    - Get rid of vhost_log_chunk_t. Just use uint8_t.
    - Implement vubr_set_log_fd_exec().
    - Kick the log if log_call_fd has been set up.
    - Mark bits in log table atomically to enable more then one
      simultaneous vhost-user backend.
    - Fix the calculations of required log table size in an
      assert.
    - Fix the coding style: only single space before assignment
      operator.
    - Add a comment on the hack to determine that queues are
      ready for processing.
    - Other minor cosmetic fixes.
v2:
    - use log_guest_addr for used ring reported by qemu instead of
      translating.
    - use mmap_size and mmap_offset defined in new
      VHOST_USER_SET_LOG_BASE interface. See the patch
      "vhost-user: modify SET_LOG_BASE to pass mmap size and
      offset".
    - start logging dirty pages only after the appropriate feature
      is set by a VHOST_USER_GET_PROTOCOL_FEATURES request.
    - updated TODO list.

 tests/vhost-user-bridge.c | 220 ++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 195 insertions(+), 25 deletions(-)

diff --git a/tests/vhost-user-bridge.c b/tests/vhost-user-bridge.c
index 864f69e..7bdfc98 100644
--- a/tests/vhost-user-bridge.c
+++ b/tests/vhost-user-bridge.c
@@ -13,16 +13,22 @@
 /*
  * TODO:
  *     - main should get parameters from the command line.
- *     - implement all request handlers.
+ *     - implement all request handlers. Still not implemented:
+ *          vubr_get_queue_num_exec()
+ *          vubr_send_rarp_exec()
  *     - test for broken requests and virtqueue.
  *     - implement features defined by Virtio 1.0 spec.
  *     - support mergeable buffers and indirect descriptors.
- *     - implement RESET_DEVICE request.
  *     - implement clean shutdown.
  *     - implement non-blocking writes to UDP backend.
  *     - implement polling strategy.
+ *     - implement clean starting/stopping of vq processing
+ *     - implement clean starting/stopping of used and buffers
+ *       dirty page logging.
  */
 
+#define _FILE_OFFSET_BITS 64
+
 #include <stddef.h>
 #include <assert.h>
 #include <stdio.h>
@@ -166,6 +172,8 @@ typedef struct VubrVirtq {
     struct vring_desc *desc;
     struct vring_avail *avail;
     struct vring_used *used;
+    uint64_t log_guest_addr;
+    int enable;
 } VubrVirtq;
 
 /* Based on qemu/hw/virtio/vhost-user.c */
@@ -173,6 +181,8 @@ typedef struct VubrVirtq {
 #define VHOST_MEMORY_MAX_NREGIONS    8
 #define VHOST_USER_F_PROTOCOL_FEATURES 30
 
+#define VHOST_LOG_PAGE 4096
+
 enum VhostUserProtocolFeature {
     VHOST_USER_PROTOCOL_F_MQ = 0,
     VHOST_USER_PROTOCOL_F_LOG_SHMFD = 1,
@@ -220,6 +230,11 @@ typedef struct VhostUserMemory {
     VhostUserMemoryRegion regions[VHOST_MEMORY_MAX_NREGIONS];
 } VhostUserMemory;
 
+typedef struct VhostUserLog {
+    uint64_t mmap_size;
+    uint64_t mmap_offset;
+} VhostUserLog;
+
 typedef struct VhostUserMsg {
     VhostUserRequest request;
 
@@ -234,6 +249,7 @@ typedef struct VhostUserMsg {
         struct vhost_vring_state state;
         struct vhost_vring_addr addr;
         VhostUserMemory memory;
+        VhostUserLog log;
     } payload;
     int fds[VHOST_MEMORY_MAX_NREGIONS];
     int fd_num;
@@ -265,8 +281,13 @@ typedef struct VubrDev {
     uint32_t nregions;
     VubrDevRegion regions[VHOST_MEMORY_MAX_NREGIONS];
     VubrVirtq vq[MAX_NR_VIRTQUEUE];
+    int log_call_fd;
+    uint64_t log_size;
+    uint8_t *log_table;
     int backend_udp_sock;
     struct sockaddr_in backend_udp_dest;
+    int ready;
+    uint64_t features;
 } VubrDev;
 
 static const char *vubr_request_str[] = {
@@ -368,7 +389,12 @@ vubr_message_read(int conn_fd, VhostUserMsg *vmsg)
 
     rc = recvmsg(conn_fd, &msg, 0);
 
-    if (rc <= 0) {
+    if (rc == 0) {
+        vubr_die("recvmsg");
+        fprintf(stderr, "Peer disconnected.\n");
+        exit(1);
+    }
+    if (rc < 0) {
         vubr_die("recvmsg");
     }
 
@@ -395,7 +421,12 @@ vubr_message_read(int conn_fd, VhostUserMsg *vmsg)
 
     if (vmsg->size) {
         rc = read(conn_fd, &vmsg->payload, vmsg->size);
-        if (rc <= 0) {
+        if (rc == 0) {
+            vubr_die("recvmsg");
+            fprintf(stderr, "Peer disconnected.\n");
+            exit(1);
+        }
+        if (rc < 0) {
             vubr_die("recvmsg");
         }
 
@@ -455,6 +486,16 @@ vubr_consume_raw_packet(VubrDev *dev, uint8_t *buf, 
uint32_t len)
     vubr_backend_udp_sendbuf(dev, buf + hdrlen, len - hdrlen);
 }
 
+/* Kick the log_call_fd if required. */
+static void
+vubr_log_kick(VubrDev *dev)
+{
+    if (dev->log_call_fd != -1) {
+        DPRINT("Kicking the QEMU's log...\n");
+        eventfd_write(dev->log_call_fd, 1);
+    }
+}
+
 /* Kick the guest if necessary. */
 static void
 vubr_virtqueue_kick(VubrVirtq *vq)
@@ -466,11 +507,39 @@ vubr_virtqueue_kick(VubrVirtq *vq)
 }
 
 static void
+vubr_log_page(uint8_t *log_table, uint64_t page)
+{
+    DPRINT("Logged dirty guest page: %"PRId64"\n", page);
+    atomic_or(&log_table[page / 8], 1 << (page % 8));
+}
+
+static void
+vubr_log_write(VubrDev *dev, uint64_t address, uint64_t length)
+{
+    uint64_t page;
+
+    if (!(dev->features & (1ULL << VHOST_F_LOG_ALL)) ||
+        !dev->log_table || !length) {
+        return;
+    }
+
+    assert(dev->log_size > ((address + length - 1) / VHOST_LOG_PAGE / 8));
+
+    page = address / VHOST_LOG_PAGE;
+    while (page * VHOST_LOG_PAGE < address + length) {
+        vubr_log_page(dev->log_table, page);
+        page += VHOST_LOG_PAGE;
+    }
+    vubr_log_kick(dev);
+}
+
+static void
 vubr_post_buffer(VubrDev *dev, VubrVirtq *vq, uint8_t *buf, int32_t len)
 {
-    struct vring_desc *desc   = vq->desc;
+    struct vring_desc *desc = vq->desc;
     struct vring_avail *avail = vq->avail;
-    struct vring_used *used   = vq->used;
+    struct vring_used *used = vq->used;
+    uint64_t log_guest_addr = vq->log_guest_addr;
 
     unsigned int size = vq->size;
 
@@ -510,6 +579,7 @@ vubr_post_buffer(VubrDev *dev, VubrVirtq *vq, uint8_t *buf, 
int32_t len)
 
     if (len <= chunk_len) {
         memcpy(chunk_start, buf, len);
+        vubr_log_write(dev, desc[i].addr, len);
     } else {
         fprintf(stderr,
                 "Received too long packet from the backend. Dropping...\n");
@@ -519,11 +589,17 @@ vubr_post_buffer(VubrDev *dev, VubrVirtq *vq, uint8_t 
*buf, int32_t len)
     /* Add descriptor to the used ring. */
     used->ring[u_index].id = d_index;
     used->ring[u_index].len = len;
+    vubr_log_write(dev,
+                   log_guest_addr + offsetof(struct vring_used, ring[u_index]),
+                   sizeof(used->ring[u_index]));
 
     vq->last_avail_index++;
     vq->last_used_index++;
 
     atomic_mb_set(&used->idx, vq->last_used_index);
+    vubr_log_write(dev,
+                   log_guest_addr + offsetof(struct vring_used, idx),
+                   sizeof(used->idx));
 
     /* Kick the guest if necessary. */
     vubr_virtqueue_kick(vq);
@@ -532,9 +608,10 @@ vubr_post_buffer(VubrDev *dev, VubrVirtq *vq, uint8_t 
*buf, int32_t len)
 static int
 vubr_process_desc(VubrDev *dev, VubrVirtq *vq)
 {
-    struct vring_desc *desc   = vq->desc;
+    struct vring_desc *desc = vq->desc;
     struct vring_avail *avail = vq->avail;
-    struct vring_used *used   = vq->used;
+    struct vring_used *used = vq->used;
+    uint64_t log_guest_addr = vq->log_guest_addr;
 
     unsigned int size = vq->size;
 
@@ -552,6 +629,8 @@ vubr_process_desc(VubrDev *dev, VubrVirtq *vq)
         void *chunk_start = (void *)gpa_to_va(dev, desc[i].addr);
         uint32_t chunk_len = desc[i].len;
 
+        assert(!(desc[i].flags & VRING_DESC_F_WRITE));
+
         if (len + chunk_len < buf_size) {
             memcpy(buf + len, chunk_start, chunk_len);
             DPRINT("%d ", chunk_len);
@@ -577,6 +656,9 @@ vubr_process_desc(VubrDev *dev, VubrVirtq *vq)
     /* Add descriptor to the used ring. */
     used->ring[u_index].id = d_index;
     used->ring[u_index].len = len;
+    vubr_log_write(dev,
+                   log_guest_addr + offsetof(struct vring_used, ring[u_index]),
+                   sizeof(used->ring[u_index]));
 
     vubr_consume_raw_packet(dev, buf, len);
 
@@ -588,6 +670,7 @@ vubr_process_avail(VubrDev *dev, VubrVirtq *vq)
 {
     struct vring_avail *avail = vq->avail;
     struct vring_used *used = vq->used;
+    uint64_t log_guest_addr = vq->log_guest_addr;
 
     while (vq->last_avail_index != atomic_mb_read(&avail->idx)) {
         vubr_process_desc(dev, vq);
@@ -596,6 +679,9 @@ vubr_process_avail(VubrDev *dev, VubrVirtq *vq)
     }
 
     atomic_mb_set(&used->idx, vq->last_used_index);
+    vubr_log_write(dev,
+                   log_guest_addr + offsetof(struct vring_used, idx),
+                   sizeof(used->idx));
 }
 
 static void
@@ -609,6 +695,10 @@ vubr_backend_recv_cb(int sock, void *ctx)
     int buflen = sizeof(buf);
     int len;
 
+    if (!dev->ready) {
+        return;
+    }
+
     DPRINT("\n\n   ***   IN UDP RECEIVE CALLBACK    ***\n\n");
 
     uint16_t avail_index = atomic_mb_read(&rx_vq->avail->idx);
@@ -656,14 +746,14 @@ vubr_get_features_exec(VubrDev *dev, VhostUserMsg *vmsg)
 {
     vmsg->payload.u64 =
             ((1ULL << VIRTIO_NET_F_MRG_RXBUF) |
-             (1ULL << VIRTIO_NET_F_CTRL_VQ) |
-             (1ULL << VIRTIO_NET_F_CTRL_RX) |
-             (1ULL << VHOST_F_LOG_ALL));
+             (1ULL << VHOST_F_LOG_ALL) |
+             (1ULL << VHOST_USER_F_PROTOCOL_FEATURES));
+
     vmsg->size = sizeof(vmsg->payload.u64);
 
     DPRINT("Sending back to guest u64: 0x%016"PRIx64"\n", vmsg->payload.u64);
 
-    /* reply */
+    /* Reply */
     return 1;
 }
 
@@ -671,6 +761,7 @@ static int
 vubr_set_features_exec(VubrDev *dev, VhostUserMsg *vmsg)
 {
     DPRINT("u64: 0x%016"PRIx64"\n", vmsg->payload.u64);
+    dev->features = vmsg->payload.u64;
     return 0;
 }
 
@@ -680,10 +771,28 @@ vubr_set_owner_exec(VubrDev *dev, VhostUserMsg *vmsg)
     return 0;
 }
 
+static void
+vubr_close_log(VubrDev *dev)
+{
+    if (dev->log_table) {
+        if (munmap(dev->log_table, dev->log_size) != 0) {
+            vubr_die("munmap()");
+        }
+
+        dev->log_table = 0;
+    }
+    if (dev->log_call_fd != -1) {
+        close(dev->log_call_fd);
+        dev->log_call_fd = -1;
+    }
+}
+
 static int
 vubr_reset_device_exec(VubrDev *dev, VhostUserMsg *vmsg)
 {
-    DPRINT("Function %s() not implemented yet.\n", __func__);
+    vubr_close_log(dev);
+    dev->ready = 0;
+    dev->features = 0;
     return 0;
 }
 
@@ -710,9 +819,9 @@ vubr_set_mem_table_exec(VubrDev *dev, VhostUserMsg *vmsg)
         DPRINT("    mmap_offset      0x%016"PRIx64"\n",
                msg_region->mmap_offset);
 
-        dev_region->gpa         = msg_region->guest_phys_addr;
-        dev_region->size        = msg_region->memory_size;
-        dev_region->qva         = msg_region->userspace_addr;
+        dev_region->gpa = msg_region->guest_phys_addr;
+        dev_region->size = msg_region->memory_size;
+        dev_region->qva = msg_region->userspace_addr;
         dev_region->mmap_offset = msg_region->mmap_offset;
 
         /* We don't use offset argument of mmap() since the
@@ -736,14 +845,38 @@ vubr_set_mem_table_exec(VubrDev *dev, VhostUserMsg *vmsg)
 static int
 vubr_set_log_base_exec(VubrDev *dev, VhostUserMsg *vmsg)
 {
-    DPRINT("Function %s() not implemented yet.\n", __func__);
-    return 0;
+    int fd;
+    uint64_t log_mmap_size, log_mmap_offset;
+    void *rc;
+
+    assert(vmsg->fd_num == 1);
+    fd = vmsg->fds[0];
+
+    assert(vmsg->size == sizeof(vmsg->payload.log));
+    log_mmap_offset = vmsg->payload.log.mmap_offset;
+    log_mmap_size = vmsg->payload.log.mmap_size;
+    DPRINT("Log mmap_offset: %"PRId64"\n", log_mmap_offset);
+    DPRINT("Log mmap_size:   %"PRId64"\n", log_mmap_size);
+
+    rc = mmap(0, log_mmap_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd,
+              log_mmap_offset);
+    if (rc == MAP_FAILED) {
+        vubr_die("mmap");
+    }
+    dev->log_table = rc;
+    dev->log_size = log_mmap_size;
+
+    vmsg->size = sizeof(vmsg->payload.u64);
+    /* Reply */
+    return 1;
 }
 
 static int
 vubr_set_log_fd_exec(VubrDev *dev, VhostUserMsg *vmsg)
 {
-    DPRINT("Function %s() not implemented yet.\n", __func__);
+    assert(vmsg->fd_num == 1);
+    dev->log_call_fd = vmsg->fds[0];
+    DPRINT("Got log_call_fd: %d\n", vmsg->fds[0]);
     return 0;
 }
 
@@ -777,6 +910,7 @@ vubr_set_vring_addr_exec(VubrDev *dev, VhostUserMsg *vmsg)
     vq->desc = (struct vring_desc *)qva_to_va(dev, vra->desc_user_addr);
     vq->used = (struct vring_used *)qva_to_va(dev, vra->used_user_addr);
     vq->avail = (struct vring_avail *)qva_to_va(dev, vra->avail_user_addr);
+    vq->log_guest_addr = vra->log_guest_addr;
 
     DPRINT("Setting virtq addresses:\n");
     DPRINT("    vring_desc  at %p\n", vq->desc);
@@ -803,8 +937,18 @@ vubr_set_vring_base_exec(VubrDev *dev, VhostUserMsg *vmsg)
 static int
 vubr_get_vring_base_exec(VubrDev *dev, VhostUserMsg *vmsg)
 {
-    DPRINT("Function %s() not implemented yet.\n", __func__);
-    return 0;
+    unsigned int index = vmsg->payload.state.index;
+
+    DPRINT("State.index: %d\n", index);
+    vmsg->payload.state.num = dev->vq[index].last_avail_index;
+    vmsg->size = sizeof(vmsg->payload.state);
+    /* FIXME: this is a work-around for a bug in QEMU enabling
+     * too early vrings. When protocol features are enabled,
+     * we have to respect * VHOST_USER_SET_VRING_ENABLE request. */
+    dev->ready = 0;
+
+    /* Reply */
+    return 1;
 }
 
 static int
@@ -829,7 +973,17 @@ vubr_set_vring_kick_exec(VubrDev *dev, VhostUserMsg *vmsg)
         DPRINT("Waiting for kicks on fd: %d for vq: %d\n",
                dev->vq[index].kick_fd, index);
     }
+    /* We temporarily use this hack to determine that both TX and RX
+     * queues are set up and ready for processing.
+     * FIXME: we need to rely in VHOST_USER_SET_VRING_ENABLE and
+     * actual kicks. */
+    if (dev->vq[0].kick_fd != -1 &&
+        dev->vq[1].kick_fd != -1) {
+        dev->ready = 1;
+        DPRINT("vhost-user-bridge is ready for processing queues.\n");
+    }
     return 0;
+
 }
 
 static int
@@ -858,9 +1012,12 @@ vubr_set_vring_err_exec(VubrDev *dev, VhostUserMsg *vmsg)
 static int
 vubr_get_protocol_features_exec(VubrDev *dev, VhostUserMsg *vmsg)
 {
-    /* FIXME: unimplented */
+    vmsg->payload.u64 = 1ULL << VHOST_USER_PROTOCOL_F_LOG_SHMFD;
     DPRINT("u64: 0x%016"PRIx64"\n", vmsg->payload.u64);
-    return 0;
+    vmsg->size = sizeof(vmsg->payload.u64);
+
+    /* Reply */
+    return 1;
 }
 
 static int
@@ -881,7 +1038,12 @@ vubr_get_queue_num_exec(VubrDev *dev, VhostUserMsg *vmsg)
 static int
 vubr_set_vring_enable_exec(VubrDev *dev, VhostUserMsg *vmsg)
 {
-    DPRINT("Function %s() not implemented yet.\n", __func__);
+    unsigned int index = vmsg->payload.state.index;
+    unsigned int enable = vmsg->payload.state.num;
+
+    DPRINT("State.index: %d\n", index);
+    DPRINT("State.enable:   %d\n", enable);
+    dev->vq[index].enable = enable;
     return 0;
 }
 
@@ -987,7 +1149,7 @@ vubr_accept_cb(int sock, void *ctx)
     socklen_t len = sizeof(un);
 
     conn_fd = accept(sock, (struct sockaddr *) &un, &len);
-    if (conn_fd  == -1) {
+    if (conn_fd == -1) {
         vubr_die("accept()");
     }
     DPRINT("Got connection from remote peer on sock %d\n", conn_fd);
@@ -1009,9 +1171,17 @@ vubr_new(const char *path)
             .size = 0,
             .last_avail_index = 0, .last_used_index = 0,
             .desc = 0, .avail = 0, .used = 0,
+            .enable = 0,
         };
     }
 
+    /* Init log */
+    dev->log_call_fd = -1;
+    dev->log_size = 0;
+    dev->log_table = 0;
+    dev->ready = 0;
+    dev->features = 0;
+
     /* Get a UNIX socket. */
     dev->sock = socket(AF_UNIX, SOCK_STREAM, 0);
     if (dev->sock == -1) {
-- 
--Victor