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Message-ID: <20101202192616.GL2085@linux.vnet.ibm.com>
Date: Thu, 2 Dec 2010 11:26:16 -0800
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
rusty@...tcorp.com.au, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] vhost test module
On Thu, Dec 02, 2010 at 09:11:30PM +0200, Michael S. Tsirkin wrote:
> On Thu, Dec 02, 2010 at 11:00:37AM -0800, Paul E. McKenney wrote:
> > On Mon, Nov 29, 2010 at 07:09:01PM +0200, Michael S. Tsirkin wrote:
> > > This adds a test module for vhost infrastructure.
> > > Intentionally not tied to kbuild to prevent people
> > > from installing and loading it accidentally.
> > >
> > > Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> >
> > On question below.
> >
> > > ---
> > >
> > > diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
> > > new file mode 100644
> > > index 0000000..099f302
> > > --- /dev/null
> > > +++ b/drivers/vhost/test.c
> > > @@ -0,0 +1,320 @@
> > > +/* Copyright (C) 2009 Red Hat, Inc.
> > > + * Author: Michael S. Tsirkin <mst@...hat.com>
> > > + *
> > > + * This work is licensed under the terms of the GNU GPL, version 2.
> > > + *
> > > + * test virtio server in host kernel.
> > > + */
> > > +
> > > +#include <linux/compat.h>
> > > +#include <linux/eventfd.h>
> > > +#include <linux/vhost.h>
> > > +#include <linux/miscdevice.h>
> > > +#include <linux/module.h>
> > > +#include <linux/mutex.h>
> > > +#include <linux/workqueue.h>
> > > +#include <linux/rcupdate.h>
> > > +#include <linux/file.h>
> > > +#include <linux/slab.h>
> > > +
> > > +#include "test.h"
> > > +#include "vhost.c"
> > > +
> > > +/* Max number of bytes transferred before requeueing the job.
> > > + * Using this limit prevents one virtqueue from starving others. */
> > > +#define VHOST_TEST_WEIGHT 0x80000
> > > +
> > > +enum {
> > > + VHOST_TEST_VQ = 0,
> > > + VHOST_TEST_VQ_MAX = 1,
> > > +};
> > > +
> > > +struct vhost_test {
> > > + struct vhost_dev dev;
> > > + struct vhost_virtqueue vqs[VHOST_TEST_VQ_MAX];
> > > +};
> > > +
> > > +/* Expects to be always run from workqueue - which acts as
> > > + * read-size critical section for our kind of RCU. */
> > > +static void handle_vq(struct vhost_test *n)
> > > +{
> > > + struct vhost_virtqueue *vq = &n->dev.vqs[VHOST_TEST_VQ];
> > > + unsigned out, in;
> > > + int head;
> > > + size_t len, total_len = 0;
> > > + void *private;
> > > +
> > > + private = rcu_dereference_check(vq->private_data, 1);
> >
> > Any chance of a check for running in a workqueue? If I remember correctly,
> > the ->lockdep_map field in the work_struct structure allows you to create
> > the required lockdep expression.
>
> We moved away from using the workqueue to a custom kernel thread
> implementation though.
OK, then could you please add a check for "current == custom_kernel_thread"
or some such?
Thanx, Paul
> > > + if (!private)
> > > + return;
> > > +
> > > + mutex_lock(&vq->mutex);
> > > + vhost_disable_notify(vq);
> > > +
> > > + for (;;) {
> > > + head = vhost_get_vq_desc(&n->dev, vq, vq->iov,
> > > + ARRAY_SIZE(vq->iov),
> > > + &out, &in,
> > > + NULL, NULL);
> > > + /* On error, stop handling until the next kick. */
> > > + if (unlikely(head < 0))
> > > + break;
> > > + /* Nothing new? Wait for eventfd to tell us they refilled. */
> > > + if (head == vq->num) {
> > > + if (unlikely(vhost_enable_notify(vq))) {
> > > + vhost_disable_notify(vq);
> > > + continue;
> > > + }
> > > + break;
> > > + }
> > > + if (in) {
> > > + vq_err(vq, "Unexpected descriptor format for TX: "
> > > + "out %d, int %d\n", out, in);
> > > + break;
> > > + }
> > > + len = iov_length(vq->iov, out);
> > > + /* Sanity check */
> > > + if (!len) {
> > > + vq_err(vq, "Unexpected 0 len for TX\n");
> > > + break;
> > > + }
> > > + vhost_add_used_and_signal(&n->dev, vq, head, 0);
> > > + total_len += len;
> > > + if (unlikely(total_len >= VHOST_TEST_WEIGHT)) {
> > > + vhost_poll_queue(&vq->poll);
> > > + break;
> > > + }
> > > + }
> > > +
> > > + mutex_unlock(&vq->mutex);
> > > +}
> > > +
> > > +static void handle_vq_kick(struct vhost_work *work)
> > > +{
> > > + struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
> > > + poll.work);
> > > + struct vhost_test *n = container_of(vq->dev, struct vhost_test, dev);
> > > +
> > > + handle_vq(n);
> > > +}
> > > +
> > > +static int vhost_test_open(struct inode *inode, struct file *f)
> > > +{
> > > + struct vhost_test *n = kmalloc(sizeof *n, GFP_KERNEL);
> > > + struct vhost_dev *dev;
> > > + int r;
> > > +
> > > + if (!n)
> > > + return -ENOMEM;
> > > +
> > > + dev = &n->dev;
> > > + n->vqs[VHOST_TEST_VQ].handle_kick = handle_vq_kick;
> > > + r = vhost_dev_init(dev, n->vqs, VHOST_TEST_VQ_MAX);
> > > + if (r < 0) {
> > > + kfree(n);
> > > + return r;
> > > + }
> > > +
> > > + f->private_data = n;
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +static void *vhost_test_stop_vq(struct vhost_test *n,
> > > + struct vhost_virtqueue *vq)
> > > +{
> > > + void *private;
> > > +
> > > + mutex_lock(&vq->mutex);
> > > + private = rcu_dereference_protected(vq->private_data,
> > > + lockdep_is_held(&vq->mutex));
> > > + rcu_assign_pointer(vq->private_data, NULL);
> > > + mutex_unlock(&vq->mutex);
> > > + return private;
> > > +}
> > > +
> > > +static void vhost_test_stop(struct vhost_test *n, void **privatep)
> > > +{
> > > + *privatep = vhost_test_stop_vq(n, n->vqs + VHOST_TEST_VQ);
> > > +}
> > > +
> > > +static void vhost_test_flush_vq(struct vhost_test *n, int index)
> > > +{
> > > + vhost_poll_flush(&n->dev.vqs[index].poll);
> > > +}
> > > +
> > > +static void vhost_test_flush(struct vhost_test *n)
> > > +{
> > > + vhost_test_flush_vq(n, VHOST_TEST_VQ);
> > > +}
> > > +
> > > +static int vhost_test_release(struct inode *inode, struct file *f)
> > > +{
> > > + struct vhost_test *n = f->private_data;
> > > + void *private;
> > > +
> > > + vhost_test_stop(n, &private);
> > > + vhost_test_flush(n);
> > > + vhost_dev_cleanup(&n->dev);
> > > + /* We do an extra flush before freeing memory,
> > > + * since jobs can re-queue themselves. */
> > > + vhost_test_flush(n);
> > > + kfree(n);
> > > + return 0;
> > > +}
> > > +
> > > +static long vhost_test_run(struct vhost_test *n, int test)
> > > +{
> > > + void *priv, *oldpriv;
> > > + struct vhost_virtqueue *vq;
> > > + int r, index;
> > > +
> > > + if (test < 0 || test > 1)
> > > + return -EINVAL;
> > > +
> > > + mutex_lock(&n->dev.mutex);
> > > + r = vhost_dev_check_owner(&n->dev);
> > > + if (r)
> > > + goto err;
> > > +
> > > + for (index = 0; index < n->dev.nvqs; ++index) {
> > > + /* Verify that ring has been setup correctly. */
> > > + if (!vhost_vq_access_ok(&n->vqs[index])) {
> > > + r = -EFAULT;
> > > + goto err;
> > > + }
> > > + }
> > > +
> > > + for (index = 0; index < n->dev.nvqs; ++index) {
> > > + vq = n->vqs + index;
> > > + mutex_lock(&vq->mutex);
> > > + priv = test ? n : NULL;
> > > +
> > > + /* start polling new socket */
> > > + oldpriv = rcu_dereference_protected(vq->private_data,
> > > + lockdep_is_held(&vq->mutex));
> > > + rcu_assign_pointer(vq->private_data, priv);
> > > +
> > > + mutex_unlock(&vq->mutex);
> > > +
> > > + if (oldpriv) {
> > > + vhost_test_flush_vq(n, index);
> > > + }
> > > + }
> > > +
> > > + mutex_unlock(&n->dev.mutex);
> > > + return 0;
> > > +
> > > +err:
> > > + mutex_unlock(&n->dev.mutex);
> > > + return r;
> > > +}
> > > +
> > > +static long vhost_test_reset_owner(struct vhost_test *n)
> > > +{
> > > + void *priv = NULL;
> > > + long err;
> > > + mutex_lock(&n->dev.mutex);
> > > + err = vhost_dev_check_owner(&n->dev);
> > > + if (err)
> > > + goto done;
> > > + vhost_test_stop(n, &priv);
> > > + vhost_test_flush(n);
> > > + err = vhost_dev_reset_owner(&n->dev);
> > > +done:
> > > + mutex_unlock(&n->dev.mutex);
> > > + return err;
> > > +}
> > > +
> > > +static int vhost_test_set_features(struct vhost_test *n, u64 features)
> > > +{
> > > + 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);
> > > + mutex_unlock(&n->dev.mutex);
> > > + return 0;
> > > +}
> > > +
> > > +static long vhost_test_ioctl(struct file *f, unsigned int ioctl,
> > > + unsigned long arg)
> > > +{
> > > + struct vhost_test *n = f->private_data;
> > > + void __user *argp = (void __user *)arg;
> > > + u64 __user *featurep = argp;
> > > + int test;
> > > + u64 features;
> > > + int r;
> > > + switch (ioctl) {
> > > + case VHOST_TEST_RUN:
> > > + if (copy_from_user(&test, argp, sizeof test))
> > > + return -EFAULT;
> > > + return vhost_test_run(n, test);
> > > + case VHOST_GET_FEATURES:
> > > + features = VHOST_FEATURES;
> > > + if (copy_to_user(featurep, &features, sizeof features))
> > > + return -EFAULT;
> > > + return 0;
> > > + case VHOST_SET_FEATURES:
> > > + if (copy_from_user(&features, featurep, sizeof features))
> > > + return -EFAULT;
> > > + if (features & ~VHOST_FEATURES)
> > > + return -EOPNOTSUPP;
> > > + return vhost_test_set_features(n, features);
> > > + case VHOST_RESET_OWNER:
> > > + return vhost_test_reset_owner(n);
> > > + default:
> > > + mutex_lock(&n->dev.mutex);
> > > + r = vhost_dev_ioctl(&n->dev, ioctl, arg);
> > > + vhost_test_flush(n);
> > > + mutex_unlock(&n->dev.mutex);
> > > + return r;
> > > + }
> > > +}
> > > +
> > > +#ifdef CONFIG_COMPAT
> > > +static long vhost_test_compat_ioctl(struct file *f, unsigned int ioctl,
> > > + unsigned long arg)
> > > +{
> > > + return vhost_test_ioctl(f, ioctl, (unsigned long)compat_ptr(arg));
> > > +}
> > > +#endif
> > > +
> > > +static const struct file_operations vhost_test_fops = {
> > > + .owner = THIS_MODULE,
> > > + .release = vhost_test_release,
> > > + .unlocked_ioctl = vhost_test_ioctl,
> > > +#ifdef CONFIG_COMPAT
> > > + .compat_ioctl = vhost_test_compat_ioctl,
> > > +#endif
> > > + .open = vhost_test_open,
> > > + .llseek = noop_llseek,
> > > +};
> > > +
> > > +static struct miscdevice vhost_test_misc = {
> > > + MISC_DYNAMIC_MINOR,
> > > + "vhost-test",
> > > + &vhost_test_fops,
> > > +};
> > > +
> > > +static int vhost_test_init(void)
> > > +{
> > > + return misc_register(&vhost_test_misc);
> > > +}
> > > +module_init(vhost_test_init);
> > > +
> > > +static void vhost_test_exit(void)
> > > +{
> > > + misc_deregister(&vhost_test_misc);
> > > +}
> > > +module_exit(vhost_test_exit);
> > > +
> > > +MODULE_VERSION("0.0.1");
> > > +MODULE_LICENSE("GPL v2");
> > > +MODULE_AUTHOR("Michael S. Tsirkin");
> > > +MODULE_DESCRIPTION("Host kernel side for virtio simulator");
> > > diff --git a/drivers/vhost/test.h b/drivers/vhost/test.h
> > > new file mode 100644
> > > index 0000000..1fef5df
> > > --- /dev/null
> > > +++ b/drivers/vhost/test.h
> > > @@ -0,0 +1,7 @@
> > > +#ifndef LINUX_VHOST_TEST_H
> > > +#define LINUX_VHOST_TEST_H
> > > +
> > > +/* Start a given test on the virtio null device. 0 stops all tests. */
> > > +#define VHOST_TEST_RUN _IOW(VHOST_VIRTIO, 0x31, int)
> > > +
> > > +#endif
> > > diff --git a/tools/virtio/vhost_test/Makefile b/tools/virtio/vhost_test/Makefile
> > > new file mode 100644
> > > index 0000000..a1d35b8
> > > --- /dev/null
> > > +++ b/tools/virtio/vhost_test/Makefile
> > > @@ -0,0 +1,2 @@
> > > +obj-m += vhost_test.o
> > > +EXTRA_CFLAGS += -Idrivers/vhost
> > > diff --git a/tools/virtio/vhost_test/vhost_test.c b/tools/virtio/vhost_test/vhost_test.c
> > > new file mode 100644
> > > index 0000000..1873518
> > > --- /dev/null
> > > +++ b/tools/virtio/vhost_test/vhost_test.c
> > > @@ -0,0 +1 @@
> > > +#include "test.c"
> > > --
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