Re: vhost changes (batched) in linux-next after 12/13 trigger random crashes in KVM guests after reboot

[Eugenio Pérez <eperezma@xxxxxxxxxx>]

Can we try with this traces?

>From b793b4106085ab1970bdedb340e49f37843ed585 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Eugenio=20P=C3=A9rez?= <eperezma@xxxxxxxxxx>
Date: Thu, 13 Feb 2020 17:27:05 +0100
Subject: [PATCH] vhost: Add debug in ioctl calls

---
 drivers/vhost/net.c   | 20 +++++++++++++++++---
 drivers/vhost/vhost.c | 16 ++++++++++++++--
 2 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index e158159671fa..e4d5f843f9c0 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -1505,10 +1505,13 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
 
 	mutex_lock(&n->dev.mutex);
 	r = vhost_dev_check_owner(&n->dev);
-	if (r)
+	if (r) {
+		pr_debug("vhost_dev_check_owner index=%u fd=%d rc r=%d", index, fd, r);
 		goto err;
+	}
 
 	if (index >= VHOST_NET_VQ_MAX) {
+		pr_debug("vhost_dev_check_owner index=%u fd=%d MAX=%d", index, fd, VHOST_NET_VQ_MAX);
 		r = -ENOBUFS;
 		goto err;
 	}
@@ -1518,22 +1521,26 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
 
 	/* Verify that ring has been setup correctly. */
 	if (!vhost_vq_access_ok(vq)) {
+		pr_debug("vhost_net_set_backend index=%u fd=%d !vhost_vq_access_ok", index, fd);
 		r = -EFAULT;
 		goto err_vq;
 	}
 	sock = get_socket(fd);
 	if (IS_ERR(sock)) {
 		r = PTR_ERR(sock);
+		pr_debug("vhost_net_set_backend index=%u fd=%d get_socket err r=%d", index, fd, r);
 		goto err_vq;
 	}
 
 	/* start polling new socket */
 	oldsock = vq->private_data;
 	if (sock != oldsock) {
+		pr_debug("sock=%p != oldsock=%p index=%u fd=%d vq=%p", sock, oldsock, index, fd, vq);
 		ubufs = vhost_net_ubuf_alloc(vq,
 					     sock && vhost_sock_zcopy(sock));
 		if (IS_ERR(ubufs)) {
 			r = PTR_ERR(ubufs);
+			pr_debug("ubufs index=%u fd=%d err r=%d vq=%p", index, fd, r, vq);
 			goto err_ubufs;
 		}
 
@@ -1541,11 +1548,15 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
 		vq->private_data = sock;
 		vhost_net_buf_unproduce(nvq);
 		r = vhost_vq_init_access(vq);
-		if (r)
+		if (r) {
+			pr_debug("init_access index=%u fd=%d r=%d vq=%p", index, fd, r, vq);
 			goto err_used;
+		}
 		r = vhost_net_enable_vq(n, vq);
-		if (r)
+		if (r) {
+			pr_debug("enable_vq index=%u fd=%d r=%d vq=%p", index, fd, r, vq);
 			goto err_used;
+		}
 		if (index == VHOST_NET_VQ_RX)
 			nvq->rx_ring = get_tap_ptr_ring(fd);
 
@@ -1559,6 +1570,8 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
 
 	mutex_unlock(&vq->mutex);
 
+	pr_debug("sock=%p", sock);
+
 	if (oldubufs) {
 		vhost_net_ubuf_put_wait_and_free(oldubufs);
 		mutex_lock(&vq->mutex);
@@ -1710,6 +1723,7 @@ static long vhost_net_ioctl(struct file *f, unsigned int ioctl,
 
 	switch (ioctl) {
 	case VHOST_NET_SET_BACKEND:
+		pr_debug("VHOST_NET_SET_BACKEND");
 		if (copy_from_user(&backend, argp, sizeof backend))
 			return -EFAULT;
 		return vhost_net_set_backend(n, backend.index, backend.fd);
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 021d70bed015..7f4848f9cec3 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1642,18 +1642,30 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
 			r = -EINVAL;
 			break;
 		}
+
+		if (vq->last_avail_idx || vq->avail_idx) {
+			pr_debug(
+				"strange VHOST_SET_VRING_BASE [vq=%p][s.index=%u][s.num=%u]",
+				vq, s.index, s.num);
+			dump_stack();
+			r = 0;
+			break;
+		}
 		vq->last_avail_idx = s.num;
 		/* Forget the cached index value. */
 		vq->avail_idx = vq->last_avail_idx;
 		pr_debug(
-			"VHOST_SET_VRING_BASE [vq=%p][vq->last_avail_idx=%u][vq->avail_idx=%u]",
-			vq, vq->last_avail_idx, vq->avail_idx);
+			"VHOST_SET_VRING_BASE [vq=%p][vq->last_avail_idx=%u][vq->avail_idx=%u][s.index=%u][s.num=%u]",
+			vq, vq->last_avail_idx, vq->avail_idx, s.index, s.num);
 		break;
 	case VHOST_GET_VRING_BASE:
 		s.index = idx;
 		s.num = vq->last_avail_idx;
 		if (copy_to_user(argp, &s, sizeof s))
 			r = -EFAULT;
+		pr_debug(
+			"VHOST_GET_VRING_BASE [vq=%p][vq->last_avail_idx=%u][vq->avail_idx=%u][s.index=%u][s.num=%u]",
+			vq, vq->last_avail_idx, vq->avail_idx, s.index, s.num);
 		break;
 	case VHOST_SET_VRING_KICK:
 		if (copy_from_user(&f, argp, sizeof f)) {
-- 
2.18.1