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Michael S. Tsirkin

2014-Jun-05 10:44 UTC

[PATCH 1/2] vhost: move acked_features to VQs

Refactor code to make sure features are only accessed
under VQ mutex. This makes everything simpler, no need
for RCU here anymore.

Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
---

This is on top of the recent pull request that I sent.

 drivers/vhost/vhost.h | 11 +++--------
 drivers/vhost/net.c   |  8 +++-----
 drivers/vhost/scsi.c  | 22 +++++++++++++---------
 drivers/vhost/test.c  |  9 ++++++---
 drivers/vhost/vhost.c | 31 ++++++++++++++++---------------
 5 files changed, 41 insertions(+), 40 deletions(-)

diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 35eeb2a..ff454a0 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -105,6 +105,7 @@ struct vhost_virtqueue {
 	struct vring_used_elem *heads;
 	/* Protected by virtqueue mutex. */
 	void *private_data;
+	unsigned acked_features;
 	/* Log write descriptors */
 	void __user *log_base;
 	struct vhost_log *log;
@@ -117,7 +118,6 @@ struct vhost_dev {
 	struct vhost_memory __rcu *memory;
 	struct mm_struct *mm;
 	struct mutex mutex;
-	unsigned acked_features;
 	struct vhost_virtqueue **vqs;
 	int nvqs;
 	struct file *log_file;
@@ -174,13 +174,8 @@ enum {
 			 (1ULL << VHOST_F_LOG_ALL),
 };
 
-static inline int vhost_has_feature(struct vhost_dev *dev, int bit)
+static inline int vhost_has_feature(struct vhost_virtqueue *vq, int bit)
 {
-	unsigned acked_features;
-
-	/* TODO: check that we are running from vhost_worker or dev mutex is
-	 * held? */
-	acked_features = rcu_dereference_index_check(dev->acked_features, 1);
-	return acked_features & (1 << bit);
+	return vq->acked_features & (1 << bit);
 }
 #endif
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index e489161..7635b59 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -585,9 +585,9 @@ static void handle_rx(struct vhost_net *net)
 	vhost_hlen = nvq->vhost_hlen;
 	sock_hlen = nvq->sock_hlen;
 
-	vq_log = unlikely(vhost_has_feature(&net->dev, VHOST_F_LOG_ALL)) ?
+	vq_log = unlikely(vhost_has_feature(vq, VHOST_F_LOG_ALL)) ?
 		vq->log : NULL;
-	mergeable = vhost_has_feature(&net->dev, VIRTIO_NET_F_MRG_RXBUF);
+	mergeable = vhost_has_feature(vq, VIRTIO_NET_F_MRG_RXBUF);
 
 	while ((sock_len = peek_head_len(sock->sk))) {
 		sock_len += sock_hlen;
@@ -1051,15 +1051,13 @@ static int vhost_net_set_features(struct vhost_net *n,
u64 features)
 		mutex_unlock(&n->dev.mutex);
 		return -EFAULT;
 	}
-	n->dev.acked_features = features;
-	smp_wmb();
 	for (i = 0; i < VHOST_NET_VQ_MAX; ++i) {
 		mutex_lock(&n->vqs[i].vq.mutex);
+		n->vqs[i].acked_features = features;
 		n->vqs[i].vhost_hlen = vhost_hlen;
 		n->vqs[i].sock_hlen = sock_hlen;
 		mutex_unlock(&n->vqs[i].vq.mutex);
 	}
-	vhost_net_flush(n);
 	mutex_unlock(&n->dev.mutex);
 	return 0;
 }
diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index cf50ce9..f1f284f 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -1373,6 +1373,9 @@ err_dev:
 
 static int vhost_scsi_set_features(struct vhost_scsi *vs, u64 features)
 {
+	struct vhost_virtqueue *vq;
+	int i;
+
 	if (features & ~VHOST_SCSI_FEATURES)
 		return -EOPNOTSUPP;
 
@@ -1382,9 +1385,13 @@ static int vhost_scsi_set_features(struct vhost_scsi *vs,
u64 features)
 		mutex_unlock(&vs->dev.mutex);
 		return -EFAULT;
 	}
-	vs->dev.acked_features = features;
-	smp_wmb();
-	vhost_scsi_flush(vs);
+
+	for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) {
+		vq = &vs->vqs[i].vq;
+		mutex_lock(&vq->mutex);
+		vq->acked_features = features;
+		mutex_unlock(&vq->mutex);
+	}
 	mutex_unlock(&vs->dev.mutex);
 	return 0;
 }
@@ -1591,10 +1598,6 @@ tcm_vhost_do_plug(struct tcm_vhost_tpg *tpg,
 		return;
 
 	mutex_lock(&vs->dev.mutex);
-	if (!vhost_has_feature(&vs->dev, VIRTIO_SCSI_F_HOTPLUG)) {
-		mutex_unlock(&vs->dev.mutex);
-		return;
-	}
 
 	if (plug)
 		reason = VIRTIO_SCSI_EVT_RESET_RESCAN;
@@ -1603,8 +1606,9 @@ tcm_vhost_do_plug(struct tcm_vhost_tpg *tpg,
 
 	vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;
 	mutex_lock(&vq->mutex);
-	tcm_vhost_send_evt(vs, tpg, lun,
-			VIRTIO_SCSI_T_TRANSPORT_RESET, reason);
+	if (vhost_has_feature(vq, VIRTIO_SCSI_F_HOTPLUG))
+		tcm_vhost_send_evt(vs, tpg, lun,
+				   VIRTIO_SCSI_T_TRANSPORT_RESET, reason);
 	mutex_unlock(&vq->mutex);
 	mutex_unlock(&vs->dev.mutex);
 }
diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
index c2a54fb..6fa3bf8 100644
--- a/drivers/vhost/test.c
+++ b/drivers/vhost/test.c
@@ -241,15 +241,18 @@ done:
 
 static int vhost_test_set_features(struct vhost_test *n, u64 features)
 {
+	struct vhost_virtqueue *vq;
+
 	mutex_lock(&n->dev.mutex);
 	if ((features & (1 << VHOST_F_LOG_ALL)) &&
 	    !vhost_log_access_ok(&n->dev)) {
 		mutex_unlock(&n->dev.mutex);
 		return -EFAULT;
 	}
-	n->dev.acked_features = features;
-	smp_wmb();
-	vhost_test_flush(n);
+	vq = &n->vqs[VHOST_TEST_VQ];
+	mutex_lock(&vq->mutex);
+	vq->acked_features = features;
+	mutex_unlock(&vq->mutex);
 	mutex_unlock(&n->dev.mutex);
 	return 0;
 }
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 1c05e60..9183f0b 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -524,11 +524,13 @@ static int memory_access_ok(struct vhost_dev *d, struct
vhost_memory *mem,
 
 	for (i = 0; i < d->nvqs; ++i) {
 		int ok;
+		bool log;
+
 		mutex_lock(&d->vqs[i]->mutex);
+		log = log_all || vhost_has_feature(d->vqs[i], VHOST_F_LOG_ALL);
 		/* If ring is inactive, will check when it's enabled. */
 		if (d->vqs[i]->private_data)
-			ok = vq_memory_access_ok(d->vqs[i]->log_base, mem,
-						 log_all);
+			ok = vq_memory_access_ok(d->vqs[i]->log_base, mem, log);
 		else
 			ok = 1;
 		mutex_unlock(&d->vqs[i]->mutex);
@@ -538,12 +540,12 @@ static int memory_access_ok(struct vhost_dev *d, struct
vhost_memory *mem,
 	return 1;
 }
 
-static int vq_access_ok(struct vhost_dev *d, unsigned int num,
+static int vq_access_ok(struct vhost_virtqueue *vq, unsigned int num,
 			struct vring_desc __user *desc,
 			struct vring_avail __user *avail,
 			struct vring_used __user *used)
 {
-	size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
+	size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
 	return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
 	       access_ok(VERIFY_READ, avail,
 			 sizeof *avail + num * sizeof *avail->ring + s) &&
@@ -565,16 +567,16 @@ EXPORT_SYMBOL_GPL(vhost_log_access_ok);
 
 /* Verify access for write logging. */
 /* Caller should have vq mutex and device mutex */
-static int vq_log_access_ok(struct vhost_dev *d, struct vhost_virtqueue *vq,
+static int vq_log_access_ok(struct vhost_virtqueue *vq,
 			    void __user *log_base)
 {
 	struct vhost_memory *mp;
-	size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
+	size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
 
 	mp = rcu_dereference_protected(vq->dev->memory,
 				       lockdep_is_held(&vq->mutex));
 	return vq_memory_access_ok(log_base, mp,
-			    vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
+				   vhost_has_feature(vq, VHOST_F_LOG_ALL)) &&
 		(!vq->log_used || log_access_ok(log_base, vq->log_addr,
 					sizeof *vq->used +
 					vq->num * sizeof *vq->used->ring + s));
@@ -584,8 +586,8 @@ static int vq_log_access_ok(struct vhost_dev *d, struct
vhost_virtqueue *vq,
 /* Caller should have vq mutex and device mutex */
 int vhost_vq_access_ok(struct vhost_virtqueue *vq)
 {
-	return vq_access_ok(vq->dev, vq->num, vq->desc, vq->avail,
vq->used) &&
-		vq_log_access_ok(vq->dev, vq, vq->log_base);
+	return vq_access_ok(vq, vq->num, vq->desc, vq->avail, vq->used)
&&
+		vq_log_access_ok(vq, vq->log_base);
 }
 EXPORT_SYMBOL_GPL(vhost_vq_access_ok);
 
@@ -612,8 +614,7 @@ static long vhost_set_memory(struct vhost_dev *d, struct
vhost_memory __user *m)
 		return -EFAULT;
 	}
 
-	if (!memory_access_ok(d, newmem,
-			      vhost_has_feature(d, VHOST_F_LOG_ALL))) {
+	if (!memory_access_ok(d, newmem, 0)) {
 		kfree(newmem);
 		return -EFAULT;
 	}
@@ -1434,11 +1435,11 @@ static bool vhost_notify(struct vhost_dev *dev, struct
vhost_virtqueue *vq)
 	 * interrupts. */
 	smp_mb();
 
-	if (vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY) &&
+	if (vhost_has_feature(vq, VIRTIO_F_NOTIFY_ON_EMPTY) &&
 	    unlikely(vq->avail_idx == vq->last_avail_idx))
 		return true;
 
-	if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
+	if (!vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX)) {
 		__u16 flags;
 		if (__get_user(flags, &vq->avail->flags)) {
 			vq_err(vq, "Failed to get flags");
@@ -1499,7 +1500,7 @@ bool vhost_enable_notify(struct vhost_dev *dev, struct
vhost_virtqueue *vq)
 	if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
 		return false;
 	vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
-	if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
+	if (!vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX)) {
 		r = vhost_update_used_flags(vq);
 		if (r) {
 			vq_err(vq, "Failed to enable notification at %p: %d\n",
@@ -1536,7 +1537,7 @@ void vhost_disable_notify(struct vhost_dev *dev, struct
vhost_virtqueue *vq)
 	if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
 		return;
 	vq->used_flags |= VRING_USED_F_NO_NOTIFY;
-	if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
+	if (!vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX)) {
 		r = vhost_update_used_flags(vq);
 		if (r)
 			vq_err(vq, "Failed to enable notification at %p: %d\n",
-- 
MST

Michael S. Tsirkin

2014-Jun-05 10:44 UTC

head link

[PATCH 2/2] vhost: move memory pointer to VQs

commit 2ae76693b8bcabf370b981cd00c36cd41d33fabc
    vhost: replace rcu with mutex
replaced rcu sync for memory accesses with VQ mutex locl/unlock.
This is correct since all accesses are under VQ mutex, but incomplete:
we still do useless rcu lock/unlock operations, someone might copy this
code into some other context where this won't be right.
This use of RCU is also non standard and hard to understand.
Let's copy the pointer to each VQ structure, this way
the access rules become straight-forward, and there's
no need for RCU anymore.

Reported-by: Eric Dumazet <eric.dumazet at gmail.com>
Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
---

This is on top of the recent pull request that I sent,
including the commit above.


 drivers/vhost/vhost.h |  8 +++-----
 drivers/vhost/net.c   |  4 ++--
 drivers/vhost/scsi.c  |  4 ++--
 drivers/vhost/test.c  |  2 +-
 drivers/vhost/vhost.c | 54 ++++++++++++++++++++++-----------------------------
 5 files changed, 31 insertions(+), 41 deletions(-)

diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index ff454a0..3eda654 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -104,6 +104,7 @@ struct vhost_virtqueue {
 	struct iovec *indirect;
 	struct vring_used_elem *heads;
 	/* Protected by virtqueue mutex. */
+	struct vhost_memory *memory;
 	void *private_data;
 	unsigned acked_features;
 	/* Log write descriptors */
@@ -112,10 +113,7 @@ struct vhost_virtqueue {
 };
 
 struct vhost_dev {
-	/* Readers use RCU to access memory table pointer
-	 * log base pointer and features.
-	 * Writers use mutex below.*/
-	struct vhost_memory __rcu *memory;
+	struct vhost_memory *memory;
 	struct mm_struct *mm;
 	struct mutex mutex;
 	struct vhost_virtqueue **vqs;
@@ -140,7 +138,7 @@ long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void
__user *argp);
 int vhost_vq_access_ok(struct vhost_virtqueue *vq);
 int vhost_log_access_ok(struct vhost_dev *);
 
-int vhost_get_vq_desc(struct vhost_dev *, struct vhost_virtqueue *,
+int vhost_get_vq_desc(struct vhost_virtqueue *,
 		      struct iovec iov[], unsigned int iov_count,
 		      unsigned int *out_num, unsigned int *in_num,
 		      struct vhost_log *log, unsigned int *log_num);
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 7635b59..3807f71 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -374,7 +374,7 @@ static void handle_tx(struct vhost_net *net)
 			      % UIO_MAXIOV == nvq->done_idx))
 			break;
 
-		head = vhost_get_vq_desc(&net->dev, vq, vq->iov,
+		head = vhost_get_vq_desc(vq, vq->iov,
 					 ARRAY_SIZE(vq->iov),
 					 &out, &in,
 					 NULL, NULL);
@@ -506,7 +506,7 @@ static int get_rx_bufs(struct vhost_virtqueue *vq,
 			r = -ENOBUFS;
 			goto err;
 		}
-		r = vhost_get_vq_desc(vq->dev, vq, vq->iov + seg,
+		r = vhost_get_vq_desc(vq, vq->iov + seg,
 				      ARRAY_SIZE(vq->iov) - seg, &out,
 				      &in, log, log_num);
 		if (unlikely(r < 0))
diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index f1f284f..83b834b 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -606,7 +606,7 @@ tcm_vhost_do_evt_work(struct vhost_scsi *vs, struct
tcm_vhost_evt *evt)
 
 again:
 	vhost_disable_notify(&vs->dev, vq);
-	head = vhost_get_vq_desc(&vs->dev, vq, vq->iov,
+	head = vhost_get_vq_desc(vq, vq->iov,
 			ARRAY_SIZE(vq->iov), &out, &in,
 			NULL, NULL);
 	if (head < 0) {
@@ -945,7 +945,7 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct
vhost_virtqueue *vq)
 	vhost_disable_notify(&vs->dev, vq);
 
 	for (;;) {
-		head = vhost_get_vq_desc(&vs->dev, vq, vq->iov,
+		head = vhost_get_vq_desc(vq, vq->iov,
 					ARRAY_SIZE(vq->iov), &out, &in,
 					NULL, NULL);
 		pr_debug("vhost_get_vq_desc: head: %d, out: %u in: %u\n",
diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
index 6fa3bf8..d9c501e 100644
--- a/drivers/vhost/test.c
+++ b/drivers/vhost/test.c
@@ -53,7 +53,7 @@ static void handle_vq(struct vhost_test *n)
 	vhost_disable_notify(&n->dev, vq);
 
 	for (;;) {
-		head = vhost_get_vq_desc(&n->dev, vq, vq->iov,
+		head = vhost_get_vq_desc(vq, vq->iov,
 					 ARRAY_SIZE(vq->iov),
 					 &out, &in,
 					 NULL, NULL);
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 9183f0b..c80609b 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -18,7 +18,6 @@
 #include <linux/mmu_context.h>
 #include <linux/miscdevice.h>
 #include <linux/mutex.h>
-#include <linux/rcupdate.h>
 #include <linux/poll.h>
 #include <linux/file.h>
 #include <linux/highmem.h>
@@ -198,6 +197,7 @@ static void vhost_vq_reset(struct vhost_dev *dev,
 	vq->call_ctx = NULL;
 	vq->call = NULL;
 	vq->log_ctx = NULL;
+	vq->memory = NULL;
 }
 
 static int vhost_worker(void *data)
@@ -419,7 +419,12 @@ void vhost_dev_reset_owner(struct vhost_dev *dev, struct
vhost_memory *memory)
 
 	/* Restore memory to default empty mapping. */
 	memory->nregions = 0;
-	RCU_INIT_POINTER(dev->memory, memory);
+	dev->memory = memory;
+	/* We don't need VQ locks below since vhost_dev_cleanup makes sure
+	 * VQs aren't running.
+	 */
+	for (i = 0; i < dev->nvqs; ++i)
+		dev->vqs[i]->memory = memory;
 }
 EXPORT_SYMBOL_GPL(vhost_dev_reset_owner);
 
@@ -462,10 +467,8 @@ void vhost_dev_cleanup(struct vhost_dev *dev, bool locked)
 		fput(dev->log_file);
 	dev->log_file = NULL;
 	/* No one will access memory at this point */
-	kfree(rcu_dereference_protected(dev->memory,
-					locked =-						lockdep_is_held(&dev->mutex)));
-	RCU_INIT_POINTER(dev->memory, NULL);
+	kfree(dev->memory);
+	dev->memory = NULL;
 	WARN_ON(!list_empty(&dev->work_list));
 	if (dev->worker) {
 		kthread_stop(dev->worker);
@@ -557,11 +560,7 @@ static int vq_access_ok(struct vhost_virtqueue *vq,
unsigned int num,
 /* Caller should have device mutex but not vq mutex */
 int vhost_log_access_ok(struct vhost_dev *dev)
 {
-	struct vhost_memory *mp;
-
-	mp = rcu_dereference_protected(dev->memory,
-				       lockdep_is_held(&dev->mutex));
-	return memory_access_ok(dev, mp, 1);
+	return memory_access_ok(dev, dev->memory, 1);
 }
 EXPORT_SYMBOL_GPL(vhost_log_access_ok);
 
@@ -573,9 +572,7 @@ static int vq_log_access_ok(struct vhost_virtqueue *vq,
 	struct vhost_memory *mp;
 	size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
 
-	mp = rcu_dereference_protected(vq->dev->memory,
-				       lockdep_is_held(&vq->mutex));
-	return vq_memory_access_ok(log_base, mp,
+	return vq_memory_access_ok(log_base, vq->memory,
 				   vhost_has_feature(vq, VHOST_F_LOG_ALL)) &&
 		(!vq->log_used || log_access_ok(log_base, vq->log_addr,
 					sizeof *vq->used +
@@ -618,15 +615,13 @@ static long vhost_set_memory(struct vhost_dev *d, struct
vhost_memory __user *m)
 		kfree(newmem);
 		return -EFAULT;
 	}
-	oldmem = rcu_dereference_protected(d->memory,
-					   lockdep_is_held(&d->mutex));
-	rcu_assign_pointer(d->memory, newmem);
+	oldmem = d->memory;
+	d->memory = newmem;
 
-	/* All memory accesses are done under some VQ mutex.
-	 * So below is a faster equivalent of synchronize_rcu()
-	 */
+	/* All memory accesses are done under some VQ mutex. */
 	for (i = 0; i < d->nvqs; ++i) {
 		mutex_lock(&d->vqs[i]->mutex);
+		d->vqs[i]->memory = newmem;
 		mutex_unlock(&d->vqs[i]->mutex);
 	}
 	kfree(oldmem);
@@ -1053,7 +1048,7 @@ int vhost_init_used(struct vhost_virtqueue *vq)
 }
 EXPORT_SYMBOL_GPL(vhost_init_used);
 
-static int translate_desc(struct vhost_dev *dev, u64 addr, u32 len,
+static int translate_desc(struct vhost_virtqueue *vq, u64 addr, u32 len,
 			  struct iovec iov[], int iov_size)
 {
 	const struct vhost_memory_region *reg;
@@ -1062,9 +1057,7 @@ static int translate_desc(struct vhost_dev *dev, u64 addr,
u32 len,
 	u64 s = 0;
 	int ret = 0;
 
-	rcu_read_lock();
-
-	mem = rcu_dereference(dev->memory);
+	mem = vq->memory;
 	while ((u64)len > s) {
 		u64 size;
 		if (unlikely(ret >= iov_size)) {
@@ -1086,7 +1079,6 @@ static int translate_desc(struct vhost_dev *dev, u64 addr,
u32 len,
 		++ret;
 	}
 
-	rcu_read_unlock();
 	return ret;
 }
 
@@ -1111,7 +1103,7 @@ static unsigned next_desc(struct vring_desc *desc)
 	return next;
 }
 
-static int get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
+static int get_indirect(struct vhost_virtqueue *vq,
 			struct iovec iov[], unsigned int iov_size,
 			unsigned int *out_num, unsigned int *in_num,
 			struct vhost_log *log, unsigned int *log_num,
@@ -1130,7 +1122,7 @@ static int get_indirect(struct vhost_dev *dev, struct
vhost_virtqueue *vq,
 		return -EINVAL;
 	}
 
-	ret = translate_desc(dev, indirect->addr, indirect->len,
vq->indirect,
+	ret = translate_desc(vq, indirect->addr, indirect->len, vq->indirect,
 			     UIO_MAXIOV);
 	if (unlikely(ret < 0)) {
 		vq_err(vq, "Translation failure %d in indirect.\n", ret);
@@ -1170,7 +1162,7 @@ static int get_indirect(struct vhost_dev *dev, struct
vhost_virtqueue *vq,
 			return -EINVAL;
 		}
 
-		ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
+		ret = translate_desc(vq, desc.addr, desc.len, iov + iov_count,
 				     iov_size - iov_count);
 		if (unlikely(ret < 0)) {
 			vq_err(vq, "Translation failure %d indirect idx %d\n",
@@ -1207,7 +1199,7 @@ static int get_indirect(struct vhost_dev *dev, struct
vhost_virtqueue *vq,
  * This function returns the descriptor number found, or vq->num (which is
  * never a valid descriptor number) if none was found.  A negative code is
  * returned on error. */
-int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
+int vhost_get_vq_desc(struct vhost_virtqueue *vq,
 		      struct iovec iov[], unsigned int iov_size,
 		      unsigned int *out_num, unsigned int *in_num,
 		      struct vhost_log *log, unsigned int *log_num)
@@ -1281,7 +1273,7 @@ int vhost_get_vq_desc(struct vhost_dev *dev, struct
vhost_virtqueue *vq,
 			return -EFAULT;
 		}
 		if (desc.flags & VRING_DESC_F_INDIRECT) {
-			ret = get_indirect(dev, vq, iov, iov_size,
+			ret = get_indirect(vq, iov, iov_size,
 					   out_num, in_num,
 					   log, log_num, &desc);
 			if (unlikely(ret < 0)) {
@@ -1292,7 +1284,7 @@ int vhost_get_vq_desc(struct vhost_dev *dev, struct
vhost_virtqueue *vq,
 			continue;
 		}
 
-		ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
+		ret = translate_desc(vq, desc.addr, desc.len, iov + iov_count,
 				     iov_size - iov_count);
 		if (unlikely(ret < 0)) {
 			vq_err(vq, "Translation failure %d descriptor idx %d\n",
-- 
MST

Michael S. Tsirkin

2014-Jun-05 12:16 UTC

head link

[PATCH 1/2] vhost: move acked_features to VQs

On Thu, Jun 05, 2014 at 01:44:14PM +0300, Michael S. Tsirkin
wrote:> Refactor code to make sure features are only accessed
> under VQ mutex. This makes everything simpler, no need
> for RCU here anymore.
> 
> Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
Ouch, I sent out wrong version of the patch.
Self-NACK, will repost.
Sorry about the noise.
> ---
> 
> This is on top of the recent pull request that I sent.
> 
>  drivers/vhost/vhost.h | 11 +++--------
>  drivers/vhost/net.c   |  8 +++-----
>  drivers/vhost/scsi.c  | 22 +++++++++++++---------
>  drivers/vhost/test.c  |  9 ++++++---
>  drivers/vhost/vhost.c | 31 ++++++++++++++++---------------
>  5 files changed, 41 insertions(+), 40 deletions(-)
> 
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index 35eeb2a..ff454a0 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -105,6 +105,7 @@ struct vhost_virtqueue {
>  	struct vring_used_elem *heads;
>  	/* Protected by virtqueue mutex. */
>  	void *private_data;
> +	unsigned acked_features;
>  	/* Log write descriptors */
>  	void __user *log_base;
>  	struct vhost_log *log;
> @@ -117,7 +118,6 @@ struct vhost_dev {
>  	struct vhost_memory __rcu *memory;
>  	struct mm_struct *mm;
>  	struct mutex mutex;
> -	unsigned acked_features;
>  	struct vhost_virtqueue **vqs;
>  	int nvqs;
>  	struct file *log_file;
> @@ -174,13 +174,8 @@ enum {
>  			 (1ULL << VHOST_F_LOG_ALL),
>  };
>  
> -static inline int vhost_has_feature(struct vhost_dev *dev, int bit)
> +static inline int vhost_has_feature(struct vhost_virtqueue *vq, int bit)
>  {
> -	unsigned acked_features;
> -
> -	/* TODO: check that we are running from vhost_worker or dev mutex is
> -	 * held? */
> -	acked_features = rcu_dereference_index_check(dev->acked_features, 1);
> -	return acked_features & (1 << bit);
> +	return vq->acked_features & (1 << bit);
>  }
>  #endif
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index e489161..7635b59 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -585,9 +585,9 @@ static void handle_rx(struct vhost_net *net)
>  	vhost_hlen = nvq->vhost_hlen;
>  	sock_hlen = nvq->sock_hlen;
>  
> -	vq_log = unlikely(vhost_has_feature(&net->dev, VHOST_F_LOG_ALL)) ?
> +	vq_log = unlikely(vhost_has_feature(vq, VHOST_F_LOG_ALL)) ?
>  		vq->log : NULL;
> -	mergeable = vhost_has_feature(&net->dev, VIRTIO_NET_F_MRG_RXBUF);
> +	mergeable = vhost_has_feature(vq, VIRTIO_NET_F_MRG_RXBUF);
>  
>  	while ((sock_len = peek_head_len(sock->sk))) {
>  		sock_len += sock_hlen;
> @@ -1051,15 +1051,13 @@ static int vhost_net_set_features(struct vhost_net
*n, u64 features)
>  		mutex_unlock(&n->dev.mutex);
>  		return -EFAULT;
>  	}
> -	n->dev.acked_features = features;
> -	smp_wmb();
>  	for (i = 0; i < VHOST_NET_VQ_MAX; ++i) {
>  		mutex_lock(&n->vqs[i].vq.mutex);
> +		n->vqs[i].acked_features = features;
>  		n->vqs[i].vhost_hlen = vhost_hlen;
>  		n->vqs[i].sock_hlen = sock_hlen;
>  		mutex_unlock(&n->vqs[i].vq.mutex);
>  	}
> -	vhost_net_flush(n);
>  	mutex_unlock(&n->dev.mutex);
>  	return 0;
>  }
> diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
> index cf50ce9..f1f284f 100644
> --- a/drivers/vhost/scsi.c
> +++ b/drivers/vhost/scsi.c
> @@ -1373,6 +1373,9 @@ err_dev:
>  
>  static int vhost_scsi_set_features(struct vhost_scsi *vs, u64 features)
>  {
> +	struct vhost_virtqueue *vq;
> +	int i;
> +
>  	if (features & ~VHOST_SCSI_FEATURES)
>  		return -EOPNOTSUPP;
>  
> @@ -1382,9 +1385,13 @@ static int vhost_scsi_set_features(struct vhost_scsi
*vs, u64 features)
>  		mutex_unlock(&vs->dev.mutex);
>  		return -EFAULT;
>  	}
> -	vs->dev.acked_features = features;
> -	smp_wmb();
> -	vhost_scsi_flush(vs);
> +
> +	for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) {
> +		vq = &vs->vqs[i].vq;
> +		mutex_lock(&vq->mutex);
> +		vq->acked_features = features;
> +		mutex_unlock(&vq->mutex);
> +	}
>  	mutex_unlock(&vs->dev.mutex);
>  	return 0;
>  }
> @@ -1591,10 +1598,6 @@ tcm_vhost_do_plug(struct tcm_vhost_tpg *tpg,
>  		return;
>  
>  	mutex_lock(&vs->dev.mutex);
> -	if (!vhost_has_feature(&vs->dev, VIRTIO_SCSI_F_HOTPLUG)) {
> -		mutex_unlock(&vs->dev.mutex);
> -		return;
> -	}
>  
>  	if (plug)
>  		reason = VIRTIO_SCSI_EVT_RESET_RESCAN;
> @@ -1603,8 +1606,9 @@ tcm_vhost_do_plug(struct tcm_vhost_tpg *tpg,
>  
>  	vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;
>  	mutex_lock(&vq->mutex);
> -	tcm_vhost_send_evt(vs, tpg, lun,
> -			VIRTIO_SCSI_T_TRANSPORT_RESET, reason);
> +	if (vhost_has_feature(vq, VIRTIO_SCSI_F_HOTPLUG))
> +		tcm_vhost_send_evt(vs, tpg, lun,
> +				   VIRTIO_SCSI_T_TRANSPORT_RESET, reason);
>  	mutex_unlock(&vq->mutex);
>  	mutex_unlock(&vs->dev.mutex);
>  }
> diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
> index c2a54fb..6fa3bf8 100644
> --- a/drivers/vhost/test.c
> +++ b/drivers/vhost/test.c
> @@ -241,15 +241,18 @@ done:
>  
>  static int vhost_test_set_features(struct vhost_test *n, u64 features)
>  {
> +	struct vhost_virtqueue *vq;
> +
>  	mutex_lock(&n->dev.mutex);
>  	if ((features & (1 << VHOST_F_LOG_ALL)) &&
>  	    !vhost_log_access_ok(&n->dev)) {
>  		mutex_unlock(&n->dev.mutex);
>  		return -EFAULT;
>  	}
> -	n->dev.acked_features = features;
> -	smp_wmb();
> -	vhost_test_flush(n);
> +	vq = &n->vqs[VHOST_TEST_VQ];
> +	mutex_lock(&vq->mutex);
> +	vq->acked_features = features;
> +	mutex_unlock(&vq->mutex);
>  	mutex_unlock(&n->dev.mutex);
>  	return 0;
>  }
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 1c05e60..9183f0b 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -524,11 +524,13 @@ static int memory_access_ok(struct vhost_dev *d,
struct vhost_memory *mem,
>  
>  	for (i = 0; i < d->nvqs; ++i) {
>  		int ok;
> +		bool log;
> +
>  		mutex_lock(&d->vqs[i]->mutex);
> +		log = log_all || vhost_has_feature(d->vqs[i], VHOST_F_LOG_ALL);
>  		/* If ring is inactive, will check when it's enabled. */
>  		if (d->vqs[i]->private_data)
> -			ok = vq_memory_access_ok(d->vqs[i]->log_base, mem,
> -						 log_all);
> +			ok = vq_memory_access_ok(d->vqs[i]->log_base, mem, log);
>  		else
>  			ok = 1;
>  		mutex_unlock(&d->vqs[i]->mutex);
> @@ -538,12 +540,12 @@ static int memory_access_ok(struct vhost_dev *d,
struct vhost_memory *mem,
>  	return 1;
>  }
>  
> -static int vq_access_ok(struct vhost_dev *d, unsigned int num,
> +static int vq_access_ok(struct vhost_virtqueue *vq, unsigned int num,
>  			struct vring_desc __user *desc,
>  			struct vring_avail __user *avail,
>  			struct vring_used __user *used)
>  {
> -	size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
> +	size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
>  	return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
>  	       access_ok(VERIFY_READ, avail,
>  			 sizeof *avail + num * sizeof *avail->ring + s) &&
> @@ -565,16 +567,16 @@ EXPORT_SYMBOL_GPL(vhost_log_access_ok);
>  
>  /* Verify access for write logging. */
>  /* Caller should have vq mutex and device mutex */
> -static int vq_log_access_ok(struct vhost_dev *d, struct vhost_virtqueue
*vq,
> +static int vq_log_access_ok(struct vhost_virtqueue *vq,
>  			    void __user *log_base)
>  {
>  	struct vhost_memory *mp;
> -	size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
> +	size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
>  
>  	mp = rcu_dereference_protected(vq->dev->memory,
>  				       lockdep_is_held(&vq->mutex));
>  	return vq_memory_access_ok(log_base, mp,
> -			    vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
> +				   vhost_has_feature(vq, VHOST_F_LOG_ALL)) &&
>  		(!vq->log_used || log_access_ok(log_base, vq->log_addr,
>  					sizeof *vq->used +
>  					vq->num * sizeof *vq->used->ring + s));
> @@ -584,8 +586,8 @@ static int vq_log_access_ok(struct vhost_dev *d, struct
vhost_virtqueue *vq,
>  /* Caller should have vq mutex and device mutex */
>  int vhost_vq_access_ok(struct vhost_virtqueue *vq)
>  {
> -	return vq_access_ok(vq->dev, vq->num, vq->desc, vq->avail,
vq->used) &&
> -		vq_log_access_ok(vq->dev, vq, vq->log_base);
> +	return vq_access_ok(vq, vq->num, vq->desc, vq->avail,
vq->used) &&
> +		vq_log_access_ok(vq, vq->log_base);
>  }
>  EXPORT_SYMBOL_GPL(vhost_vq_access_ok);
>  
> @@ -612,8 +614,7 @@ static long vhost_set_memory(struct vhost_dev *d,
struct vhost_memory __user *m)
>  		return -EFAULT;
>  	}
>  
> -	if (!memory_access_ok(d, newmem,
> -			      vhost_has_feature(d, VHOST_F_LOG_ALL))) {
> +	if (!memory_access_ok(d, newmem, 0)) {
>  		kfree(newmem);
>  		return -EFAULT;
>  	}
> @@ -1434,11 +1435,11 @@ static bool vhost_notify(struct vhost_dev *dev,
struct vhost_virtqueue *vq)
>  	 * interrupts. */
>  	smp_mb();
>  
> -	if (vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY) &&
> +	if (vhost_has_feature(vq, VIRTIO_F_NOTIFY_ON_EMPTY) &&
>  	    unlikely(vq->avail_idx == vq->last_avail_idx))
>  		return true;
>  
> -	if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
> +	if (!vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX)) {
>  		__u16 flags;
>  		if (__get_user(flags, &vq->avail->flags)) {
>  			vq_err(vq, "Failed to get flags");
> @@ -1499,7 +1500,7 @@ bool vhost_enable_notify(struct vhost_dev *dev,
struct vhost_virtqueue *vq)
>  	if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
>  		return false;
>  	vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
> -	if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
> +	if (!vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX)) {
>  		r = vhost_update_used_flags(vq);
>  		if (r) {
>  			vq_err(vq, "Failed to enable notification at %p: %d\n",
> @@ -1536,7 +1537,7 @@ void vhost_disable_notify(struct vhost_dev *dev,
struct vhost_virtqueue *vq)
>  	if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
>  		return;
>  	vq->used_flags |= VRING_USED_F_NO_NOTIFY;
> -	if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
> +	if (!vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX)) {
>  		r = vhost_update_used_flags(vq);
>  		if (r)
>  			vq_err(vq, "Failed to enable notification at %p: %d\n",
> -- 
> MST
>

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