linux/drivers/xen/evtchn.c
Rahul Singh 58f6259b7a xen/evtchn: Introduce new IOCTL to bind static evtchn
Xen 4.17 supports the creation of static evtchns. To allow user space
application to bind static evtchns introduce new ioctl
"IOCTL_EVTCHN_BIND_STATIC". Existing IOCTL doing more than binding
that’s why we need to introduce the new IOCTL to only bind the static
event channels.

Static evtchns to be available for use during the lifetime of the
guest. When the application exits, __unbind_from_irq() ends up being
called from release() file operations because of that static evtchns
are getting closed. To avoid closing the static event channel, add the
new bool variable "is_static" in "struct irq_info" to mark the event
channel static when creating the event channel to avoid closing the
static evtchn.

Also, take this opportunity to remove the open-coded version of the
evtchn close in drivers/xen/evtchn.c file and use xen_evtchn_close().

Signed-off-by: Rahul Singh <rahul.singh@arm.com>
Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>
Link: https://lore.kernel.org/r/ae7329bf1713f83e4aad4f3fa0f316258c40a3e9.1689677042.git.rahul.singh@arm.com
Signed-off-by: Juergen Gross <jgross@suse.com>
2023-07-26 08:42:34 +02:00

727 lines
16 KiB
C

/******************************************************************************
* evtchn.c
*
* Driver for receiving and demuxing event-channel signals.
*
* Copyright (c) 2004-2005, K A Fraser
* Multi-process extensions Copyright (c) 2004, Steven Smith
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation; or, when distributed
* separately from the Linux kernel or incorporated into other
* software packages, subject to the following license:
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this source file (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use, copy, modify,
* merge, publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/major.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/poll.h>
#include <linux/irq.h>
#include <linux/init.h>
#include <linux/mutex.h>
#include <linux/cpu.h>
#include <linux/mm.h>
#include <linux/vmalloc.h>
#include <xen/xen.h>
#include <xen/events.h>
#include <xen/evtchn.h>
#include <xen/xen-ops.h>
#include <asm/xen/hypervisor.h>
struct per_user_data {
struct mutex bind_mutex; /* serialize bind/unbind operations */
struct rb_root evtchns;
unsigned int nr_evtchns;
/* Notification ring, accessed via /dev/xen/evtchn. */
unsigned int ring_size;
evtchn_port_t *ring;
unsigned int ring_cons, ring_prod, ring_overflow;
struct mutex ring_cons_mutex; /* protect against concurrent readers */
spinlock_t ring_prod_lock; /* product against concurrent interrupts */
/* Processes wait on this queue when ring is empty. */
wait_queue_head_t evtchn_wait;
struct fasync_struct *evtchn_async_queue;
const char *name;
domid_t restrict_domid;
};
#define UNRESTRICTED_DOMID ((domid_t)-1)
struct user_evtchn {
struct rb_node node;
struct per_user_data *user;
evtchn_port_t port;
bool enabled;
};
static void evtchn_free_ring(evtchn_port_t *ring)
{
kvfree(ring);
}
static unsigned int evtchn_ring_offset(struct per_user_data *u,
unsigned int idx)
{
return idx & (u->ring_size - 1);
}
static evtchn_port_t *evtchn_ring_entry(struct per_user_data *u,
unsigned int idx)
{
return u->ring + evtchn_ring_offset(u, idx);
}
static int add_evtchn(struct per_user_data *u, struct user_evtchn *evtchn)
{
struct rb_node **new = &(u->evtchns.rb_node), *parent = NULL;
u->nr_evtchns++;
while (*new) {
struct user_evtchn *this;
this = rb_entry(*new, struct user_evtchn, node);
parent = *new;
if (this->port < evtchn->port)
new = &((*new)->rb_left);
else if (this->port > evtchn->port)
new = &((*new)->rb_right);
else
return -EEXIST;
}
/* Add new node and rebalance tree. */
rb_link_node(&evtchn->node, parent, new);
rb_insert_color(&evtchn->node, &u->evtchns);
return 0;
}
static void del_evtchn(struct per_user_data *u, struct user_evtchn *evtchn)
{
u->nr_evtchns--;
rb_erase(&evtchn->node, &u->evtchns);
kfree(evtchn);
}
static struct user_evtchn *find_evtchn(struct per_user_data *u,
evtchn_port_t port)
{
struct rb_node *node = u->evtchns.rb_node;
while (node) {
struct user_evtchn *evtchn;
evtchn = rb_entry(node, struct user_evtchn, node);
if (evtchn->port < port)
node = node->rb_left;
else if (evtchn->port > port)
node = node->rb_right;
else
return evtchn;
}
return NULL;
}
static irqreturn_t evtchn_interrupt(int irq, void *data)
{
struct user_evtchn *evtchn = data;
struct per_user_data *u = evtchn->user;
unsigned int prod, cons;
WARN(!evtchn->enabled,
"Interrupt for port %u, but apparently not enabled; per-user %p\n",
evtchn->port, u);
evtchn->enabled = false;
spin_lock(&u->ring_prod_lock);
prod = READ_ONCE(u->ring_prod);
cons = READ_ONCE(u->ring_cons);
if ((prod - cons) < u->ring_size) {
*evtchn_ring_entry(u, prod) = evtchn->port;
smp_wmb(); /* Ensure ring contents visible */
WRITE_ONCE(u->ring_prod, prod + 1);
if (cons == prod) {
wake_up_interruptible(&u->evtchn_wait);
kill_fasync(&u->evtchn_async_queue,
SIGIO, POLL_IN);
}
} else
u->ring_overflow = 1;
spin_unlock(&u->ring_prod_lock);
return IRQ_HANDLED;
}
static ssize_t evtchn_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
int rc;
unsigned int c, p, bytes1 = 0, bytes2 = 0;
struct per_user_data *u = file->private_data;
/* Whole number of ports. */
count &= ~(sizeof(evtchn_port_t)-1);
if (count == 0)
return 0;
if (count > PAGE_SIZE)
count = PAGE_SIZE;
for (;;) {
mutex_lock(&u->ring_cons_mutex);
rc = -EFBIG;
if (u->ring_overflow)
goto unlock_out;
c = READ_ONCE(u->ring_cons);
p = READ_ONCE(u->ring_prod);
if (c != p)
break;
mutex_unlock(&u->ring_cons_mutex);
if (file->f_flags & O_NONBLOCK)
return -EAGAIN;
rc = wait_event_interruptible(u->evtchn_wait,
READ_ONCE(u->ring_cons) != READ_ONCE(u->ring_prod));
if (rc)
return rc;
}
/* Byte lengths of two chunks. Chunk split (if any) is at ring wrap. */
if (((c ^ p) & u->ring_size) != 0) {
bytes1 = (u->ring_size - evtchn_ring_offset(u, c)) *
sizeof(evtchn_port_t);
bytes2 = evtchn_ring_offset(u, p) * sizeof(evtchn_port_t);
} else {
bytes1 = (p - c) * sizeof(evtchn_port_t);
bytes2 = 0;
}
/* Truncate chunks according to caller's maximum byte count. */
if (bytes1 > count) {
bytes1 = count;
bytes2 = 0;
} else if ((bytes1 + bytes2) > count) {
bytes2 = count - bytes1;
}
rc = -EFAULT;
smp_rmb(); /* Ensure that we see the port before we copy it. */
if (copy_to_user(buf, evtchn_ring_entry(u, c), bytes1) ||
((bytes2 != 0) &&
copy_to_user(&buf[bytes1], &u->ring[0], bytes2)))
goto unlock_out;
WRITE_ONCE(u->ring_cons, c + (bytes1 + bytes2) / sizeof(evtchn_port_t));
rc = bytes1 + bytes2;
unlock_out:
mutex_unlock(&u->ring_cons_mutex);
return rc;
}
static ssize_t evtchn_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
int rc, i;
evtchn_port_t *kbuf = (evtchn_port_t *)__get_free_page(GFP_KERNEL);
struct per_user_data *u = file->private_data;
if (kbuf == NULL)
return -ENOMEM;
/* Whole number of ports. */
count &= ~(sizeof(evtchn_port_t)-1);
rc = 0;
if (count == 0)
goto out;
if (count > PAGE_SIZE)
count = PAGE_SIZE;
rc = -EFAULT;
if (copy_from_user(kbuf, buf, count) != 0)
goto out;
mutex_lock(&u->bind_mutex);
for (i = 0; i < (count/sizeof(evtchn_port_t)); i++) {
evtchn_port_t port = kbuf[i];
struct user_evtchn *evtchn;
evtchn = find_evtchn(u, port);
if (evtchn && !evtchn->enabled) {
evtchn->enabled = true;
xen_irq_lateeoi(irq_from_evtchn(port), 0);
}
}
mutex_unlock(&u->bind_mutex);
rc = count;
out:
free_page((unsigned long)kbuf);
return rc;
}
static int evtchn_resize_ring(struct per_user_data *u)
{
unsigned int new_size;
evtchn_port_t *new_ring, *old_ring;
/*
* Ensure the ring is large enough to capture all possible
* events. i.e., one free slot for each bound event.
*/
if (u->nr_evtchns <= u->ring_size)
return 0;
if (u->ring_size == 0)
new_size = 64;
else
new_size = 2 * u->ring_size;
new_ring = kvmalloc_array(new_size, sizeof(*new_ring), GFP_KERNEL);
if (!new_ring)
return -ENOMEM;
old_ring = u->ring;
/*
* Access to the ring contents is serialized by either the
* prod /or/ cons lock so take both when resizing.
*/
mutex_lock(&u->ring_cons_mutex);
spin_lock_irq(&u->ring_prod_lock);
/*
* Copy the old ring contents to the new ring.
*
* To take care of wrapping, a full ring, and the new index
* pointing into the second half, simply copy the old contents
* twice.
*
* +---------+ +------------------+
* |34567 12| -> |34567 1234567 12|
* +-----p-c-+ +-------c------p---+
*/
memcpy(new_ring, old_ring, u->ring_size * sizeof(*u->ring));
memcpy(new_ring + u->ring_size, old_ring,
u->ring_size * sizeof(*u->ring));
u->ring = new_ring;
u->ring_size = new_size;
spin_unlock_irq(&u->ring_prod_lock);
mutex_unlock(&u->ring_cons_mutex);
evtchn_free_ring(old_ring);
return 0;
}
static int evtchn_bind_to_user(struct per_user_data *u, evtchn_port_t port,
bool is_static)
{
struct user_evtchn *evtchn;
int rc = 0;
/*
* Ports are never reused, so every caller should pass in a
* unique port.
*
* (Locking not necessary because we haven't registered the
* interrupt handler yet, and our caller has already
* serialized bind operations.)
*/
evtchn = kzalloc(sizeof(*evtchn), GFP_KERNEL);
if (!evtchn)
return -ENOMEM;
evtchn->user = u;
evtchn->port = port;
evtchn->enabled = true; /* start enabled */
rc = add_evtchn(u, evtchn);
if (rc < 0)
goto err;
rc = evtchn_resize_ring(u);
if (rc < 0)
goto err;
rc = bind_evtchn_to_irqhandler_lateeoi(port, evtchn_interrupt, 0,
u->name, evtchn);
if (rc < 0)
goto err;
rc = evtchn_make_refcounted(port, is_static);
return rc;
err:
/* bind failed, should close the port now */
if (!is_static)
xen_evtchn_close(port);
del_evtchn(u, evtchn);
return rc;
}
static void evtchn_unbind_from_user(struct per_user_data *u,
struct user_evtchn *evtchn)
{
int irq = irq_from_evtchn(evtchn->port);
BUG_ON(irq < 0);
unbind_from_irqhandler(irq, evtchn);
del_evtchn(u, evtchn);
}
static long evtchn_ioctl(struct file *file,
unsigned int cmd, unsigned long arg)
{
int rc;
struct per_user_data *u = file->private_data;
void __user *uarg = (void __user *) arg;
/* Prevent bind from racing with unbind */
mutex_lock(&u->bind_mutex);
switch (cmd) {
case IOCTL_EVTCHN_BIND_VIRQ: {
struct ioctl_evtchn_bind_virq bind;
struct evtchn_bind_virq bind_virq;
rc = -EACCES;
if (u->restrict_domid != UNRESTRICTED_DOMID)
break;
rc = -EFAULT;
if (copy_from_user(&bind, uarg, sizeof(bind)))
break;
bind_virq.virq = bind.virq;
bind_virq.vcpu = xen_vcpu_nr(0);
rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
&bind_virq);
if (rc != 0)
break;
rc = evtchn_bind_to_user(u, bind_virq.port, false);
if (rc == 0)
rc = bind_virq.port;
break;
}
case IOCTL_EVTCHN_BIND_INTERDOMAIN: {
struct ioctl_evtchn_bind_interdomain bind;
struct evtchn_bind_interdomain bind_interdomain;
rc = -EFAULT;
if (copy_from_user(&bind, uarg, sizeof(bind)))
break;
rc = -EACCES;
if (u->restrict_domid != UNRESTRICTED_DOMID &&
u->restrict_domid != bind.remote_domain)
break;
bind_interdomain.remote_dom = bind.remote_domain;
bind_interdomain.remote_port = bind.remote_port;
rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_interdomain,
&bind_interdomain);
if (rc != 0)
break;
rc = evtchn_bind_to_user(u, bind_interdomain.local_port, false);
if (rc == 0)
rc = bind_interdomain.local_port;
break;
}
case IOCTL_EVTCHN_BIND_UNBOUND_PORT: {
struct ioctl_evtchn_bind_unbound_port bind;
struct evtchn_alloc_unbound alloc_unbound;
rc = -EACCES;
if (u->restrict_domid != UNRESTRICTED_DOMID)
break;
rc = -EFAULT;
if (copy_from_user(&bind, uarg, sizeof(bind)))
break;
alloc_unbound.dom = DOMID_SELF;
alloc_unbound.remote_dom = bind.remote_domain;
rc = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound,
&alloc_unbound);
if (rc != 0)
break;
rc = evtchn_bind_to_user(u, alloc_unbound.port, false);
if (rc == 0)
rc = alloc_unbound.port;
break;
}
case IOCTL_EVTCHN_UNBIND: {
struct ioctl_evtchn_unbind unbind;
struct user_evtchn *evtchn;
rc = -EFAULT;
if (copy_from_user(&unbind, uarg, sizeof(unbind)))
break;
rc = -EINVAL;
if (unbind.port >= xen_evtchn_nr_channels())
break;
rc = -ENOTCONN;
evtchn = find_evtchn(u, unbind.port);
if (!evtchn)
break;
disable_irq(irq_from_evtchn(unbind.port));
evtchn_unbind_from_user(u, evtchn);
rc = 0;
break;
}
case IOCTL_EVTCHN_BIND_STATIC: {
struct ioctl_evtchn_bind bind;
struct user_evtchn *evtchn;
rc = -EFAULT;
if (copy_from_user(&bind, uarg, sizeof(bind)))
break;
rc = -EISCONN;
evtchn = find_evtchn(u, bind.port);
if (evtchn)
break;
rc = evtchn_bind_to_user(u, bind.port, true);
break;
}
case IOCTL_EVTCHN_NOTIFY: {
struct ioctl_evtchn_notify notify;
struct user_evtchn *evtchn;
rc = -EFAULT;
if (copy_from_user(&notify, uarg, sizeof(notify)))
break;
rc = -ENOTCONN;
evtchn = find_evtchn(u, notify.port);
if (evtchn) {
notify_remote_via_evtchn(notify.port);
rc = 0;
}
break;
}
case IOCTL_EVTCHN_RESET: {
/* Initialise the ring to empty. Clear errors. */
mutex_lock(&u->ring_cons_mutex);
spin_lock_irq(&u->ring_prod_lock);
WRITE_ONCE(u->ring_cons, 0);
WRITE_ONCE(u->ring_prod, 0);
u->ring_overflow = 0;
spin_unlock_irq(&u->ring_prod_lock);
mutex_unlock(&u->ring_cons_mutex);
rc = 0;
break;
}
case IOCTL_EVTCHN_RESTRICT_DOMID: {
struct ioctl_evtchn_restrict_domid ierd;
rc = -EACCES;
if (u->restrict_domid != UNRESTRICTED_DOMID)
break;
rc = -EFAULT;
if (copy_from_user(&ierd, uarg, sizeof(ierd)))
break;
rc = -EINVAL;
if (ierd.domid == 0 || ierd.domid >= DOMID_FIRST_RESERVED)
break;
u->restrict_domid = ierd.domid;
rc = 0;
break;
}
default:
rc = -ENOSYS;
break;
}
mutex_unlock(&u->bind_mutex);
return rc;
}
static __poll_t evtchn_poll(struct file *file, poll_table *wait)
{
__poll_t mask = EPOLLOUT | EPOLLWRNORM;
struct per_user_data *u = file->private_data;
poll_wait(file, &u->evtchn_wait, wait);
if (READ_ONCE(u->ring_cons) != READ_ONCE(u->ring_prod))
mask |= EPOLLIN | EPOLLRDNORM;
if (u->ring_overflow)
mask = EPOLLERR;
return mask;
}
static int evtchn_fasync(int fd, struct file *filp, int on)
{
struct per_user_data *u = filp->private_data;
return fasync_helper(fd, filp, on, &u->evtchn_async_queue);
}
static int evtchn_open(struct inode *inode, struct file *filp)
{
struct per_user_data *u;
u = kzalloc(sizeof(*u), GFP_KERNEL);
if (u == NULL)
return -ENOMEM;
u->name = kasprintf(GFP_KERNEL, "evtchn:%s", current->comm);
if (u->name == NULL) {
kfree(u);
return -ENOMEM;
}
init_waitqueue_head(&u->evtchn_wait);
mutex_init(&u->bind_mutex);
mutex_init(&u->ring_cons_mutex);
spin_lock_init(&u->ring_prod_lock);
u->restrict_domid = UNRESTRICTED_DOMID;
filp->private_data = u;
return stream_open(inode, filp);
}
static int evtchn_release(struct inode *inode, struct file *filp)
{
struct per_user_data *u = filp->private_data;
struct rb_node *node;
while ((node = u->evtchns.rb_node)) {
struct user_evtchn *evtchn;
evtchn = rb_entry(node, struct user_evtchn, node);
disable_irq(irq_from_evtchn(evtchn->port));
evtchn_unbind_from_user(u, evtchn);
}
evtchn_free_ring(u->ring);
kfree(u->name);
kfree(u);
return 0;
}
static const struct file_operations evtchn_fops = {
.owner = THIS_MODULE,
.read = evtchn_read,
.write = evtchn_write,
.unlocked_ioctl = evtchn_ioctl,
.poll = evtchn_poll,
.fasync = evtchn_fasync,
.open = evtchn_open,
.release = evtchn_release,
.llseek = no_llseek,
};
static struct miscdevice evtchn_miscdev = {
.minor = MISC_DYNAMIC_MINOR,
.name = "xen/evtchn",
.fops = &evtchn_fops,
};
static int __init evtchn_init(void)
{
int err;
if (!xen_domain())
return -ENODEV;
/* Create '/dev/xen/evtchn'. */
err = misc_register(&evtchn_miscdev);
if (err != 0) {
pr_err("Could not register /dev/xen/evtchn\n");
return err;
}
pr_info("Event-channel device installed\n");
return 0;
}
static void __exit evtchn_cleanup(void)
{
misc_deregister(&evtchn_miscdev);
}
module_init(evtchn_init);
module_exit(evtchn_cleanup);
MODULE_LICENSE("GPL");