[Qemu-devel] [PATCH v2] tests/vhost-user-bridge: implement logging of dirty pages

[Victor Kaplansky <victork@redhat.com>]

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 <victork@redhat.com>
---
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 | 169 ++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 155 insertions(+), 14 deletions(-)

diff --git a/tests/vhost-user-bridge.c b/tests/vhost-user-bridge.c
index fa18ad5..8c1c997 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_set_protocol_features_exec()
+ *          vubr_get_queue_num_exec()
+ *          vubr_set_vring_enable_exec()
+ *          vubr_send_rarp_exec()
+ *          vubr_set_log_fd_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.
  */
 
+#define _FILE_OFFSET_BITS 64
+
 #include <stddef.h>
 #include <assert.h>
 #include <stdio.h>
@@ -166,6 +172,7 @@ typedef struct VubrVirtq {
     struct vring_desc *desc;
     struct vring_avail *avail;
     struct vring_used *used;
+    uint64_t log_guest_addr;
 } VubrVirtq;
 
 /* Based on qemu/hw/virtio/vhost-user.c */
@@ -173,6 +180,9 @@ typedef struct VubrVirtq {
 #define VHOST_MEMORY_MAX_NREGIONS    8
 #define VHOST_USER_F_PROTOCOL_FEATURES 30
 
+typedef uint8_t vhost_log_chunk_t;
+#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;
+    vhost_log_chunk_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");
         }
 
@@ -465,12 +496,39 @@ 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);
+    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 & VHOST_F_LOG_ALL) || !dev->log_table || !length) {
+        return;
+    }
+
+    assert(dev->log_size >= ((address + length) / 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;
+    }
+}
+
 static void
 vubr_post_buffer(VubrDev *dev, VubrVirtq *vq, uint8_t *buf, int32_t len)
 {
     struct vring_desc *desc   = vq->desc;
     struct vring_avail *avail = vq->avail;
     struct vring_used *used   = vq->used;
+    uint64_t log_guest_addr = vq->log_guest_addr;
 
     unsigned int size = vq->size;
 
@@ -510,6 +568,7 @@ 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 +578,17 @@ 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);
@@ -535,6 +600,7 @@ vubr_process_desc(VubrDev *dev, VubrVirtq *vq)
     struct vring_desc *desc   = vq->desc;
     struct vring_avail *avail = vq->avail;
     struct vring_used *used   = vq->used;
+    uint64_t log_guest_addr = vq->log_guest_addr;
 
     unsigned int size = vq->size;
 
@@ -552,6 +618,8 @@ 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 +645,9 @@ 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 +659,7 @@ 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 +668,9 @@ 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 +684,10 @@ 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);
@@ -656,9 +735,9 @@ 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);
@@ -671,6 +750,7 @@ 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 +760,28 @@ 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;
 }
 
@@ -736,8 +834,30 @@ 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 = (vhost_log_chunk_t *) rc;
+    dev->log_size = log_mmap_size;
+
+    vmsg->size = sizeof(vmsg->payload.u64);
+    /* Reply */
+    return 1;
 }
 
 static int
@@ -777,6 +897,7 @@ 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 +924,14 @@ 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);
+
+    /* reply */
+    return 1;
 }
 
 static int
@@ -829,6 +956,10 @@ 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);
     }
+    if (dev->vq[0].kick_fd != -1 &&
+        dev->vq[1].kick_fd != -1) {
+        dev->ready = 1;
+    }
     return 0;
 }
 
@@ -858,9 +989,12 @@ 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
@@ -1012,6 +1146,13 @@ vubr_new(const char *path)
         };
     }
 
+    /* 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