[PATCH v3 0/2] vhost: add VDUSE reconnection support

[PATCH v3 0/2] vhost: add VDUSE reconnection support

[Maxime Coquelin]

This series adds support for VDUSE reconnection.

First patch introduces the reconnection file layout and
track the virtqueues available index updates in the
datapath and control queue.

Second patch adds VDUSE reconnect intialization and some
sanity checks to prevent incompatible reconnections.

Changes in v3:
==============
- Fixed missing avail index updates (David)
- Fixed typos in commit message (David)
- Applied R-by's

Changes in v2:
==============
- Added more sanity checks at reconnection
- Improve versionning
- Fix error loggin (Chenbo)
- Clarify why offloading device start is required (Chenbo)
- Change runtime path to <RUNPATH>/vduse instead of <RUNPATH>/dpdk/vduse

Maxime Coquelin (2):
  vhost: add logging mechanism for reconnection
  vhost: add reconnection support to VDUSE

 lib/vhost/vduse.c           | 308 +++++++++++++++++++++++++++++++-----
 lib/vhost/vhost.c           |   2 +
 lib/vhost/vhost.h           |  41 ++++-
 lib/vhost/vhost_user.c      |   4 +
 lib/vhost/virtio_net.c      |   8 +
 lib/vhost/virtio_net_ctrl.c |   2 +
 6 files changed, 322 insertions(+), 43 deletions(-)

-- 
2.46.0

[PATCH v3 1/2] vhost: add logging mechanism for reconnection

[Maxime Coquelin]

This patch introduces a way for backend to keep track
of the needed information to be able to reconnect without
frontend cooperation.

It will be used for VDUSE, which does not provide interface
for the backend to save and later recover local virtqueues
metadata needed to reconnect.

Vhost-user support could also be added for improved packed
ring reconnection support.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Chenbo Xia <chenbox@nvidia.com>
Reviewed-by: David Marchand <david.marchand@redhat.com>
---
 lib/vhost/vhost.c           |  2 ++
 lib/vhost/vhost.h           | 41 ++++++++++++++++++++++++++++++++++---
 lib/vhost/vhost_user.c      |  4 ++++
 lib/vhost/virtio_net.c      |  8 ++++++++
 lib/vhost/virtio_net_ctrl.c |  2 ++
 5 files changed, 54 insertions(+), 3 deletions(-)

diff --git a/lib/vhost/vhost.c b/lib/vhost/vhost.c
index ac71d17784..5a50a06f8d 100644
--- a/lib/vhost/vhost.c
+++ b/lib/vhost/vhost.c
@@ -1712,9 +1712,11 @@ rte_vhost_set_vring_base(int vid, uint16_t queue_id,
 		vq->avail_wrap_counter = !!(last_avail_idx & (1 << 15));
 		vq->last_used_idx = last_used_idx & 0x7fff;
 		vq->used_wrap_counter = !!(last_used_idx & (1 << 15));
+		vhost_virtqueue_reconnect_log_packed(vq);
 	} else {
 		vq->last_avail_idx = last_avail_idx;
 		vq->last_used_idx = last_used_idx;
+		vhost_virtqueue_reconnect_log_split(vq);
 	}
 
 	return 0;
diff --git a/lib/vhost/vhost.h b/lib/vhost/vhost.h
index cd3fa55f1b..1f4192f5d1 100644
--- a/lib/vhost/vhost.h
+++ b/lib/vhost/vhost.h
@@ -269,6 +269,24 @@ struct vhost_async {
 	};
 };
 
+#define VHOST_RECONNECT_VERSION		0x0
+#define VHOST_MAX_VRING			0x100
+#define VHOST_MAX_QUEUE_PAIRS		0x80
+
+struct __rte_cache_aligned vhost_reconnect_vring {
+	uint16_t last_avail_idx;
+	bool avail_wrap_counter;
+};
+
+struct vhost_reconnect_data {
+	uint32_t version;
+	uint64_t features;
+	uint8_t status;
+	struct virtio_net_config config;
+	uint32_t nr_vrings;
+	struct vhost_reconnect_vring vring[VHOST_MAX_VRING];
+};
+
 /**
  * Structure contains variables relevant to RX/TX virtqueues.
  */
@@ -351,6 +369,7 @@ struct __rte_cache_aligned vhost_virtqueue {
 	struct virtqueue_stats	stats;
 
 	RTE_ATOMIC(bool) irq_pending;
+	struct vhost_reconnect_vring *reconnect_log;
 };
 
 /* Virtio device status as per Virtio specification */
@@ -362,9 +381,6 @@ struct __rte_cache_aligned vhost_virtqueue {
 #define VIRTIO_DEVICE_STATUS_DEV_NEED_RESET	0x40
 #define VIRTIO_DEVICE_STATUS_FAILED		0x80
 
-#define VHOST_MAX_VRING			0x100
-#define VHOST_MAX_QUEUE_PAIRS		0x80
-
 /* Declare IOMMU related bits for older kernels */
 #ifndef VIRTIO_F_IOMMU_PLATFORM
 
@@ -538,8 +554,26 @@ struct __rte_cache_aligned virtio_net {
 	struct rte_vhost_user_extern_ops extern_ops;
 
 	struct vhost_backend_ops *backend_ops;
+
+	struct vhost_reconnect_data *reconnect_log;
 };
 
+static __rte_always_inline void
+vhost_virtqueue_reconnect_log_split(struct vhost_virtqueue *vq)
+{
+	if (vq->reconnect_log != NULL)
+		vq->reconnect_log->last_avail_idx = vq->last_avail_idx;
+}
+
+static __rte_always_inline void
+vhost_virtqueue_reconnect_log_packed(struct vhost_virtqueue *vq)
+{
+	if (vq->reconnect_log != NULL) {
+		vq->reconnect_log->last_avail_idx = vq->last_avail_idx;
+		vq->reconnect_log->avail_wrap_counter = vq->avail_wrap_counter;
+	}
+}
+
 static inline void
 vq_assert_lock__(struct virtio_net *dev, struct vhost_virtqueue *vq, const char *func)
 	__rte_assert_exclusive_lock(&vq->access_lock)
@@ -584,6 +618,7 @@ vq_inc_last_avail_packed(struct vhost_virtqueue *vq, uint16_t num)
 		vq->avail_wrap_counter ^= 1;
 		vq->last_avail_idx -= vq->size;
 	}
+	vhost_virtqueue_reconnect_log_packed(vq);
 }
 
 void __vhost_log_cache_write(struct virtio_net *dev,
diff --git a/lib/vhost/vhost_user.c b/lib/vhost/vhost_user.c
index 5f470da38a..d20b9e8497 100644
--- a/lib/vhost/vhost_user.c
+++ b/lib/vhost/vhost_user.c
@@ -954,6 +954,7 @@ translate_ring_addresses(struct virtio_net **pdev, struct vhost_virtqueue **pvq)
 			vq->last_used_idx, vq->used->idx);
 		vq->last_used_idx  = vq->used->idx;
 		vq->last_avail_idx = vq->used->idx;
+		vhost_virtqueue_reconnect_log_split(vq);
 		VHOST_CONFIG_LOG(dev->ifname, WARNING,
 			"some packets maybe resent for Tx and dropped for Rx");
 	}
@@ -1039,9 +1040,11 @@ vhost_user_set_vring_base(struct virtio_net **pdev,
 		 */
 		vq->last_used_idx = vq->last_avail_idx;
 		vq->used_wrap_counter = vq->avail_wrap_counter;
+		vhost_virtqueue_reconnect_log_packed(vq);
 	} else {
 		vq->last_used_idx = ctx->msg.payload.state.num;
 		vq->last_avail_idx = ctx->msg.payload.state.num;
+		vhost_virtqueue_reconnect_log_split(vq);
 	}
 
 	VHOST_CONFIG_LOG(dev->ifname, INFO,
@@ -1997,6 +2000,7 @@ vhost_check_queue_inflights_split(struct virtio_net *dev,
 	}
 
 	vq->last_avail_idx += resubmit_num;
+	vhost_virtqueue_reconnect_log_split(vq);
 
 	if (resubmit_num) {
 		resubmit = rte_zmalloc_socket("resubmit", sizeof(struct rte_vhost_resubmit_info),
diff --git a/lib/vhost/virtio_net.c b/lib/vhost/virtio_net.c
index 370402d849..f66a0c82f8 100644
--- a/lib/vhost/virtio_net.c
+++ b/lib/vhost/virtio_net.c
@@ -1445,6 +1445,7 @@ virtio_dev_rx_split(struct virtio_net *dev, struct vhost_virtqueue *vq,
 		}
 
 		vq->last_avail_idx += num_buffers;
+		vhost_virtqueue_reconnect_log_split(vq);
 	}
 
 	do_data_copy_enqueue(dev, vq);
@@ -1857,6 +1858,7 @@ virtio_dev_rx_async_submit_split(struct virtio_net *dev, struct vhost_virtqueue
 		pkts_info[slot_idx].mbuf = pkts[pkt_idx];
 
 		vq->last_avail_idx += num_buffers;
+		vhost_virtqueue_reconnect_log_split(vq);
 	}
 
 	if (unlikely(pkt_idx == 0))
@@ -1885,6 +1887,7 @@ virtio_dev_rx_async_submit_split(struct virtio_net *dev, struct vhost_virtqueue
 		/* recover shadow used ring and available ring */
 		vq->shadow_used_idx -= num_descs;
 		vq->last_avail_idx -= num_descs;
+		vhost_virtqueue_reconnect_log_split(vq);
 	}
 
 	/* keep used descriptors */
@@ -2100,6 +2103,7 @@ dma_error_handler_packed(struct vhost_virtqueue *vq, uint16_t slot_idx,
 		vq->last_avail_idx = vq->last_avail_idx + vq->size - descs_err;
 		vq->avail_wrap_counter ^= 1;
 	}
+	vhost_virtqueue_reconnect_log_packed(vq);
 
 	if (async->buffer_idx_packed >= buffers_err)
 		async->buffer_idx_packed -= buffers_err;
@@ -3182,6 +3186,7 @@ virtio_dev_tx_split(struct virtio_net *dev, struct vhost_virtqueue *vq,
 
 	if (likely(vq->shadow_used_idx)) {
 		vq->last_avail_idx += vq->shadow_used_idx;
+		vhost_virtqueue_reconnect_log_split(vq);
 		do_data_copy_dequeue(vq);
 		flush_shadow_used_ring_split(dev, vq);
 		vhost_vring_call_split(dev, vq);
@@ -3854,6 +3859,7 @@ virtio_dev_tx_async_split(struct virtio_net *dev, struct vhost_virtqueue *vq,
 		async->desc_idx_split++;
 
 		vq->last_avail_idx++;
+		vhost_virtqueue_reconnect_log_split(vq);
 	}
 
 	if (unlikely(dropped))
@@ -3872,6 +3878,7 @@ virtio_dev_tx_async_split(struct virtio_net *dev, struct vhost_virtqueue *vq,
 		pkt_idx = n_xfer;
 		/* recover available ring */
 		vq->last_avail_idx -= pkt_err;
+		vhost_virtqueue_reconnect_log_split(vq);
 
 		/**
 		 * recover async channel copy related structures and free pktmbufs
@@ -4153,6 +4160,7 @@ virtio_dev_tx_async_packed(struct virtio_net *dev, struct vhost_virtqueue *vq,
 			vq->last_avail_idx += vq->size - descs_err;
 			vq->avail_wrap_counter ^= 1;
 		}
+		vhost_virtqueue_reconnect_log_packed(vq);
 	}
 
 	async->pkts_idx += pkt_idx;
diff --git a/lib/vhost/virtio_net_ctrl.c b/lib/vhost/virtio_net_ctrl.c
index 8f78122361..b8ee94018e 100644
--- a/lib/vhost/virtio_net_ctrl.c
+++ b/lib/vhost/virtio_net_ctrl.c
@@ -169,6 +169,7 @@ virtio_net_ctrl_pop(struct virtio_net *dev, struct vhost_virtqueue *cvq,
 	cvq->last_avail_idx++;
 	if (cvq->last_avail_idx >= cvq->size)
 		cvq->last_avail_idx -= cvq->size;
+	vhost_virtqueue_reconnect_log_split(cvq);
 
 	if (dev->features & (1ULL << VIRTIO_RING_F_EVENT_IDX))
 		vhost_avail_event(cvq) = cvq->last_avail_idx;
@@ -181,6 +182,7 @@ virtio_net_ctrl_pop(struct virtio_net *dev, struct vhost_virtqueue *cvq,
 	cvq->last_avail_idx++;
 	if (cvq->last_avail_idx >= cvq->size)
 		cvq->last_avail_idx -= cvq->size;
+	vhost_virtqueue_reconnect_log_split(cvq);
 
 	if (dev->features & (1ULL << VIRTIO_RING_F_EVENT_IDX))
 		vhost_avail_event(cvq) = cvq->last_avail_idx;
-- 
2.46.0

[PATCH v3 2/2] vhost: add reconnection support to VDUSE

[Maxime Coquelin]

This patch enables VDUSE reconnection support making use of
the newly introduced reconnection mechanism in Vhost
library.

At DPDK VDUSE device creation time, there are two
possibilities:
 1. The Kernel VDUSE device does not exist:
  a. A reconnection file named after the VDUSE device name
     is created in VDUSE tmpfs.
  b. The file is truncated to 'struct vhost_reconnect_data'
     size, and mmapped.
  c. Negotiated features, Virtio status... are saved for
     sanity checks at reconnect time.
 2. The Kernel VDUSE device already exists:
  a. Exit with failure if no reconnect file exists for
     this device.
  b. Open and mmap the reconnect file.
  c. Perform sanity check to ensure features are compatible.
  d. Restore virtqueues' available indexes at startup time.

Then at runtime, the virtqueues' available index are logged by
the Vhost reconnection mechanism.

At DPDK VDUSE device destruction time, there are two
possibilities:
 1. The Kernel VDUSE device destruction succeeded, which
    means it is no more attached to the vDPA bus. The
    reconnection file is unmapped and then removed.
 2. The Kernel VDUSE device destruction failed, meaning it
    is no more attached to the vDPA bus. The reconnection
    file is unmapped but not removed to make possible later
    reconnection.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Chenbo Xia <chenbox@nvidia.com>
Reviewed-by: David Marchand <david.marchand@redhat.com>
---
 lib/vhost/vduse.c | 308 ++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 268 insertions(+), 40 deletions(-)

diff --git a/lib/vhost/vduse.c b/lib/vhost/vduse.c
index c66602905c..f9ac317438 100644
--- a/lib/vhost/vduse.c
+++ b/lib/vhost/vduse.c
@@ -136,7 +136,7 @@ vduse_control_queue_event(int fd, void *arg, int *remove __rte_unused)
 }
 
 static void
-vduse_vring_setup(struct virtio_net *dev, unsigned int index)
+vduse_vring_setup(struct virtio_net *dev, unsigned int index, bool reconnect)
 {
 	struct vhost_virtqueue *vq = dev->virtqueue[index];
 	struct vhost_vring_addr *ra = &vq->ring_addrs;
@@ -152,6 +152,19 @@ vduse_vring_setup(struct virtio_net *dev, unsigned int index)
 		return;
 	}
 
+	if (reconnect) {
+		vq->last_avail_idx = vq->reconnect_log->last_avail_idx;
+		vq->last_used_idx = vq->reconnect_log->last_avail_idx;
+	} else {
+		vq->last_avail_idx = vq_info.split.avail_index;
+		vq->last_used_idx = vq_info.split.avail_index;
+	}
+	vq->size = vq_info.num;
+	vq->ready = true;
+	vq->enabled = vq_info.ready;
+	ra->desc_user_addr = vq_info.desc_addr;
+	ra->avail_user_addr = vq_info.driver_addr;
+	ra->used_user_addr = vq_info.device_addr;
 	VHOST_CONFIG_LOG(dev->ifname, INFO, "VQ %u info:", index);
 	VHOST_CONFIG_LOG(dev->ifname, INFO, "\tnum: %u", vq_info.num);
 	VHOST_CONFIG_LOG(dev->ifname, INFO, "\tdesc_addr: %llx",
@@ -160,17 +173,9 @@ vduse_vring_setup(struct virtio_net *dev, unsigned int index)
 			(unsigned long long)vq_info.driver_addr);
 	VHOST_CONFIG_LOG(dev->ifname, INFO, "\tdevice_addr: %llx",
 			(unsigned long long)vq_info.device_addr);
-	VHOST_CONFIG_LOG(dev->ifname, INFO, "\tavail_idx: %u", vq_info.split.avail_index);
+	VHOST_CONFIG_LOG(dev->ifname, INFO, "\tavail_idx: %u", vq->last_avail_idx);
+	VHOST_CONFIG_LOG(dev->ifname, INFO, "\tused_idx: %u", vq->last_used_idx);
 	VHOST_CONFIG_LOG(dev->ifname, INFO, "\tready: %u", vq_info.ready);
-
-	vq->last_avail_idx = vq_info.split.avail_index;
-	vq->size = vq_info.num;
-	vq->ready = true;
-	vq->enabled = vq_info.ready;
-	ra->desc_user_addr = vq_info.desc_addr;
-	ra->avail_user_addr = vq_info.driver_addr;
-	ra->used_user_addr = vq_info.device_addr;
-
 	vq->kickfd = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
 	if (vq->kickfd < 0) {
 		VHOST_CONFIG_LOG(dev->ifname, ERR, "Failed to init kickfd for VQ %u: %s",
@@ -267,7 +272,7 @@ vduse_vring_cleanup(struct virtio_net *dev, unsigned int index)
 }
 
 static void
-vduse_device_start(struct virtio_net *dev)
+vduse_device_start(struct virtio_net *dev, bool reconnect)
 {
 	unsigned int i, ret;
 
@@ -287,6 +292,15 @@ vduse_device_start(struct virtio_net *dev)
 		return;
 	}
 
+	if (reconnect && dev->features != dev->reconnect_log->features) {
+		VHOST_CONFIG_LOG(dev->ifname, ERR,
+				"Mismatch between reconnect file features 0x%" PRIx64 " & device features 0x%" PRIx64,
+				dev->reconnect_log->features, dev->features);
+		return;
+	}
+
+	dev->reconnect_log->features = dev->features;
+
 	VHOST_CONFIG_LOG(dev->ifname, INFO, "Negotiated Virtio features: 0x%" PRIx64,
 		dev->features);
 
@@ -300,7 +314,7 @@ vduse_device_start(struct virtio_net *dev)
 	}
 
 	for (i = 0; i < dev->nr_vring; i++)
-		vduse_vring_setup(dev, i);
+		vduse_vring_setup(dev, i, reconnect);
 
 	dev->flags |= VIRTIO_DEV_READY;
 
@@ -373,6 +387,7 @@ vduse_events_handler(int fd, void *arg, int *remove __rte_unused)
 				req.s.status);
 		old_status = dev->status;
 		dev->status = req.s.status;
+		dev->reconnect_log->status = dev->status;
 		resp.result = VDUSE_REQ_RESULT_OK;
 		break;
 	case VDUSE_UPDATE_IOTLB:
@@ -398,7 +413,7 @@ vduse_events_handler(int fd, void *arg, int *remove __rte_unused)
 
 	if ((old_status ^ dev->status) & VIRTIO_DEVICE_STATUS_DRIVER_OK) {
 		if (dev->status & VIRTIO_DEVICE_STATUS_DRIVER_OK)
-			vduse_device_start(dev);
+			vduse_device_start(dev, false);
 		else
 			vduse_device_stop(dev);
 	}
@@ -407,10 +422,64 @@ vduse_events_handler(int fd, void *arg, int *remove __rte_unused)
 			vduse_req_id_to_str(req.type), req.type);
 }
 
+static char vduse_reconnect_dir[PATH_MAX];
+static bool vduse_reconnect_path_set;
+
+static int
+vduse_reconnect_path_init(void)
+{
+	const char *directory;
+	int ret;
+
+	/* from RuntimeDirectory= see systemd.exec */
+	directory = getenv("RUNTIME_DIRECTORY");
+	if (directory == NULL) {
+		/*
+		 * Used standard convention defined in
+		 * XDG Base Directory Specification and
+		 * Filesystem Hierarchy Standard.
+		 */
+		if (getuid() == 0)
+			directory = "/var/run";
+		else
+			directory = getenv("XDG_RUNTIME_DIR") ? : "/tmp";
+	}
+
+	ret = snprintf(vduse_reconnect_dir, sizeof(vduse_reconnect_dir), "%s/vduse",
+			directory);
+	if (ret < 0 || ret == sizeof(vduse_reconnect_dir)) {
+		VHOST_CONFIG_LOG("vduse", ERR, "Error creating VDUSE reconnect path name");
+		return -1;
+	}
+
+	ret = mkdir(vduse_reconnect_dir, 0700);
+	if (ret < 0 && errno != EEXIST) {
+		VHOST_CONFIG_LOG("vduse", ERR, "Error creating '%s': %s",
+				vduse_reconnect_dir, strerror(errno));
+		return -1;
+	}
+
+	VHOST_CONFIG_LOG("vduse", INFO, "Created VDUSE reconnect directory in %s",
+			vduse_reconnect_dir);
+
+	return 0;
+}
+
+static void
+vduse_reconnect_handler(int fd, void *arg, int *remove)
+{
+	struct virtio_net *dev = arg;
+
+	vduse_device_start(dev, true);
+
+	close(fd);
+	*remove = 1;
+}
+
 int
 vduse_device_create(const char *path, bool compliant_ol_flags)
 {
-	int control_fd, dev_fd, vid, ret;
+	int control_fd, dev_fd, vid, ret, reco_fd;
 	uint32_t i, max_queue_pairs, total_queues;
 	struct virtio_net *dev;
 	struct virtio_net_config vnet_config = {{ 0 }};
@@ -418,6 +487,9 @@ vduse_device_create(const char *path, bool compliant_ol_flags)
 	uint64_t features;
 	struct vduse_dev_config *dev_config = NULL;
 	const char *name = path + strlen("/dev/vduse/");
+	char reconnect_file[PATH_MAX];
+	struct vhost_reconnect_data *reconnect_log = NULL;
+	bool reconnect = false;
 
 	if (vduse.fdset == NULL) {
 		vduse.fdset = fdset_init("vduse-evt");
@@ -427,6 +499,20 @@ vduse_device_create(const char *path, bool compliant_ol_flags)
 		}
 	}
 
+	if (vduse_reconnect_path_set == false) {
+		if (vduse_reconnect_path_init() < 0) {
+			VHOST_CONFIG_LOG(path, ERR, "failed to initialize reconnect path");
+			return -1;
+		}
+		vduse_reconnect_path_set = true;
+	}
+
+	ret = snprintf(reconnect_file, sizeof(reconnect_file), "%s/%s", vduse_reconnect_dir, name);
+	if (ret < 0 || ret == sizeof(reconnect_file)) {
+		VHOST_CONFIG_LOG(name, ERR, "Failed to create vduse reconnect path name");
+		return -1;
+	}
+
 	control_fd = open(VDUSE_CTRL_PATH, O_RDWR);
 	if (control_fd < 0) {
 		VHOST_CONFIG_LOG(name, ERR, "Failed to open %s: %s",
@@ -441,14 +527,6 @@ vduse_device_create(const char *path, bool compliant_ol_flags)
 		goto out_ctrl_close;
 	}
 
-	dev_config = malloc(offsetof(struct vduse_dev_config, config) +
-			sizeof(vnet_config));
-	if (!dev_config) {
-		VHOST_CONFIG_LOG(name, ERR, "Failed to allocate VDUSE config");
-		ret = -1;
-		goto out_ctrl_close;
-	}
-
 	ret = rte_vhost_driver_get_features(path, &features);
 	if (ret < 0) {
 		VHOST_CONFIG_LOG(name, ERR, "Failed to get backend features");
@@ -469,23 +547,118 @@ vduse_device_create(const char *path, bool compliant_ol_flags)
 	else
 		total_queues += 1; /* Includes ctrl queue */
 
-	vnet_config.max_virtqueue_pairs = max_queue_pairs;
-	memset(dev_config, 0, sizeof(struct vduse_dev_config));
+	if (access(path, F_OK) == 0) {
+		VHOST_CONFIG_LOG(name, INFO, "Device already exists, reconnecting...");
+		reconnect = true;
+
+		reco_fd = open(reconnect_file, O_RDWR, 0600);
+		if (reco_fd < 0) {
+			if (errno == ENOENT)
+				VHOST_CONFIG_LOG(name, ERR, "Missing reconnect file (%s)",
+						reconnect_file);
+			else
+				VHOST_CONFIG_LOG(name, ERR, "Failed to open reconnect file %s (%s)",
+						reconnect_file, strerror(errno));
+			ret = -1;
+			goto out_ctrl_close;
+		}
 
-	strncpy(dev_config->name, name, VDUSE_NAME_MAX - 1);
-	dev_config->device_id = VIRTIO_ID_NET;
-	dev_config->vendor_id = 0;
-	dev_config->features = features;
-	dev_config->vq_num = total_queues;
-	dev_config->vq_align = sysconf(_SC_PAGE_SIZE);
-	dev_config->config_size = sizeof(struct virtio_net_config);
-	memcpy(dev_config->config, &vnet_config, sizeof(vnet_config));
+		reconnect_log = mmap(NULL, sizeof(*reconnect_log), PROT_READ | PROT_WRITE,
+				MAP_SHARED, reco_fd, 0);
+		close(reco_fd);
+		if (reconnect_log == MAP_FAILED) {
+			VHOST_CONFIG_LOG(name, ERR, "Failed to mmap reconnect file %s (%s)",
+					reconnect_file, strerror(errno));
+			ret = -1;
+			goto out_ctrl_close;
+		}
 
-	ret = ioctl(control_fd, VDUSE_CREATE_DEV, dev_config);
-	if (ret < 0) {
-		VHOST_CONFIG_LOG(name, ERR, "Failed to create VDUSE device: %s",
-				strerror(errno));
-		goto out_free;
+		if (reconnect_log->version != VHOST_RECONNECT_VERSION) {
+			VHOST_CONFIG_LOG(name, ERR,
+					"Version mismatch between backend (0x%x) & reconnection file (0x%x)",
+					VHOST_RECONNECT_VERSION, reconnect_log->version);
+		}
+
+		if ((reconnect_log->features & features) != reconnect_log->features) {
+			VHOST_CONFIG_LOG(name, ERR,
+					"Features mismatch between backend (0x%" PRIx64 ") & reconnection file (0x%" PRIx64 ")",
+					features, reconnect_log->features);
+			ret = -1;
+			goto out_ctrl_close;
+		}
+
+		if (reconnect_log->nr_vrings != total_queues) {
+			VHOST_CONFIG_LOG(name, ERR,
+					"Queues number mismatch between backend (%u) and reconnection file (%u)",
+					total_queues, reconnect_log->nr_vrings);
+			ret = -1;
+			goto out_ctrl_close;
+		}
+	} else {
+		reco_fd = open(reconnect_file, O_CREAT | O_EXCL | O_RDWR, 0600);
+		if (reco_fd < 0) {
+			if (errno == EEXIST) {
+				VHOST_CONFIG_LOG(name, ERR, "Reconnect file %s exists but not the device",
+						reconnect_file);
+			} else {
+				VHOST_CONFIG_LOG(name, ERR, "Failed to open reconnect file %s (%s)",
+						reconnect_file, strerror(errno));
+			}
+			ret = -1;
+			goto out_ctrl_close;
+		}
+
+		ret = ftruncate(reco_fd, sizeof(*reconnect_log));
+		if (ret < 0) {
+			VHOST_CONFIG_LOG(name, ERR, "Failed to truncate reconnect file %s (%s)",
+					reconnect_file, strerror(errno));
+			close(reco_fd);
+			goto out_ctrl_close;
+		}
+
+		reconnect_log = mmap(NULL, sizeof(*reconnect_log), PROT_READ | PROT_WRITE,
+					MAP_SHARED, reco_fd, 0);
+		close(reco_fd);
+		if (reconnect_log == MAP_FAILED) {
+			VHOST_CONFIG_LOG(name, ERR, "Failed to mmap reconnect file %s (%s)",
+					reconnect_file, strerror(errno));
+			ret = -1;
+			goto out_ctrl_close;
+		}
+
+		reconnect_log->version = VHOST_RECONNECT_VERSION;
+
+		dev_config = malloc(offsetof(struct vduse_dev_config, config) +
+				sizeof(vnet_config));
+		if (!dev_config) {
+			VHOST_CONFIG_LOG(name, ERR, "Failed to allocate VDUSE config");
+			ret = -1;
+			goto out_ctrl_close;
+		}
+
+		vnet_config.max_virtqueue_pairs = max_queue_pairs;
+		memset(dev_config, 0, sizeof(struct vduse_dev_config));
+
+		rte_strscpy(dev_config->name, name, VDUSE_NAME_MAX - 1);
+		dev_config->device_id = VIRTIO_ID_NET;
+		dev_config->vendor_id = 0;
+		dev_config->features = features;
+		dev_config->vq_num = total_queues;
+		dev_config->vq_align = sysconf(_SC_PAGE_SIZE);
+		dev_config->config_size = sizeof(struct virtio_net_config);
+		memcpy(dev_config->config, &vnet_config, sizeof(vnet_config));
+
+		ret = ioctl(control_fd, VDUSE_CREATE_DEV, dev_config);
+		if (ret < 0) {
+			VHOST_CONFIG_LOG(name, ERR, "Failed to create VDUSE device: %s",
+					strerror(errno));
+			goto out_free;
+		}
+
+		memcpy(&reconnect_log->config, &vnet_config, sizeof(vnet_config));
+		reconnect_log->nr_vrings = total_queues;
+		free(dev_config);
+		dev_config = NULL;
 	}
 
 	dev_fd = open(path, O_RDWR);
@@ -519,10 +692,15 @@ vduse_device_create(const char *path, bool compliant_ol_flags)
 	strncpy(dev->ifname, path, IF_NAME_SZ - 1);
 	dev->vduse_ctrl_fd = control_fd;
 	dev->vduse_dev_fd = dev_fd;
+	dev->reconnect_log = reconnect_log;
+	if (reconnect)
+		dev->status = dev->reconnect_log->status;
+
 	vhost_setup_virtio_net(dev->vid, true, compliant_ol_flags, true, true);
 
 	for (i = 0; i < total_queues; i++) {
 		struct vduse_vq_config vq_cfg = { 0 };
+		struct vhost_virtqueue *vq;
 
 		ret = alloc_vring_queue(dev, i);
 		if (ret) {
@@ -530,6 +708,12 @@ vduse_device_create(const char *path, bool compliant_ol_flags)
 			goto out_dev_destroy;
 		}
 
+		vq = dev->virtqueue[i];
+		vq->reconnect_log = &reconnect_log->vring[i];
+
+		if (reconnect)
+			continue;
+
 		vq_cfg.index = i;
 		vq_cfg.max_size = 1024;
 
@@ -549,7 +733,32 @@ vduse_device_create(const char *path, bool compliant_ol_flags)
 		goto out_dev_destroy;
 	}
 
-	free(dev_config);
+	if (reconnect && dev->status & VIRTIO_DEVICE_STATUS_DRIVER_OK)  {
+		/*
+		 * Make vduse_device_start() being executed in the same
+		 * context for both reconnection and fresh startup.
+		 */
+		reco_fd = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
+		if (reco_fd < 0) {
+			VHOST_CONFIG_LOG(name, ERR, "Failed to create reco_fd: %s",
+					strerror(errno));
+			ret = -1;
+			goto out_dev_destroy;
+		}
+
+		ret = fdset_add(vduse.fdset, reco_fd, vduse_reconnect_handler, NULL, dev);
+		if (ret) {
+			VHOST_CONFIG_LOG(name, ERR, "Failed to add reconnect fd %d to vduse fdset",
+					reco_fd);
+			goto out_dev_destroy;
+		}
+
+		ret = eventfd_write(reco_fd, (eventfd_t)1);
+		if (ret < 0) {
+			VHOST_CONFIG_LOG(name, ERR, "Failed to write to reconnect eventfd");
+			goto out_dev_destroy;
+		}
+	}
 
 	return 0;
 
@@ -587,6 +796,9 @@ vduse_device_destroy(const char *path)
 	if (vid == RTE_MAX_VHOST_DEVICE)
 		return -1;
 
+	if (dev->reconnect_log)
+		munmap(dev->reconnect_log, sizeof(*dev->reconnect_log));
+
 	vduse_device_stop(dev);
 
 	fdset_del(vduse.fdset, dev->vduse_dev_fd);
@@ -597,10 +809,26 @@ vduse_device_destroy(const char *path)
 	}
 
 	if (dev->vduse_ctrl_fd >= 0) {
+		char reconnect_file[PATH_MAX];
+
 		ret = ioctl(dev->vduse_ctrl_fd, VDUSE_DESTROY_DEV, name);
-		if (ret)
+		if (ret) {
 			VHOST_CONFIG_LOG(name, ERR, "Failed to destroy VDUSE device: %s",
 					strerror(errno));
+		} else {
+			/*
+			 * VDUSE device was no more attached to the vDPA bus,
+			 * so we can remove the reconnect file.
+			 */
+			ret = snprintf(reconnect_file, sizeof(reconnect_file), "%s/%s",
+					vduse_reconnect_dir, name);
+			if (ret < 0 || ret == sizeof(reconnect_file))
+				VHOST_CONFIG_LOG(name, ERR,
+						"Failed to create vduse reconnect path name");
+			else
+				unlink(reconnect_file);
+		}
+
 		close(dev->vduse_ctrl_fd);
 		dev->vduse_ctrl_fd = -1;
 	}
-- 
2.46.0

Re: [PATCH v3 0/2] vhost: add VDUSE reconnection support

[Maxime Coquelin]

On 9/23/24 21:51, Maxime Coquelin wrote:
> This series adds support for VDUSE reconnection.
> 
> First patch introduces the reconnection file layout and
> track the virtqueues available index updates in the
> datapath and control queue.
> 
> Second patch adds VDUSE reconnect intialization and some
> sanity checks to prevent incompatible reconnections.
> 
> Changes in v3:
> ==============
> - Fixed missing avail index updates (David)
> - Fixed typos in commit message (David)
> - Applied R-by's
> 
> Changes in v2:
> ==============
> - Added more sanity checks at reconnection
> - Improve versionning
> - Fix error loggin (Chenbo)
> - Clarify why offloading device start is required (Chenbo)
> - Change runtime path to <RUNPATH>/vduse instead of <RUNPATH>/dpdk/vduse
> 
> Maxime Coquelin (2):
>    vhost: add logging mechanism for reconnection
>    vhost: add reconnection support to VDUSE
> 
>   lib/vhost/vduse.c           | 308 +++++++++++++++++++++++++++++++-----
>   lib/vhost/vhost.c           |   2 +
>   lib/vhost/vhost.h           |  41 ++++-
>   lib/vhost/vhost_user.c      |   4 +
>   lib/vhost/virtio_net.c      |   8 +
>   lib/vhost/virtio_net_ctrl.c |   2 +
>   6 files changed, 322 insertions(+), 43 deletions(-)
> 

Applied to next-virtio/for-next-net