|
|
|
|
@ -2,182 +2,20 @@
|
|
|
|
|
* launcher controls and communicates with the Guest. For example,
|
|
|
|
|
* the first write will tell us the Guest's memory layout and entry
|
|
|
|
|
* point. A read will run the Guest until something happens, such as
|
|
|
|
|
* a signal or the Guest doing a NOTIFY out to the Launcher. There is
|
|
|
|
|
* also a way for the Launcher to attach eventfds to particular NOTIFY
|
|
|
|
|
* values instead of returning from the read() call.
|
|
|
|
|
* a signal or the Guest accessing a device.
|
|
|
|
|
:*/
|
|
|
|
|
#include <linux/uaccess.h>
|
|
|
|
|
#include <linux/miscdevice.h>
|
|
|
|
|
#include <linux/fs.h>
|
|
|
|
|
#include <linux/sched.h>
|
|
|
|
|
#include <linux/eventfd.h>
|
|
|
|
|
#include <linux/file.h>
|
|
|
|
|
#include <linux/slab.h>
|
|
|
|
|
#include <linux/export.h>
|
|
|
|
|
#include "lg.h"
|
|
|
|
|
|
|
|
|
|
/*L:056
|
|
|
|
|
* Before we move on, let's jump ahead and look at what the kernel does when
|
|
|
|
|
* it needs to look up the eventfds. That will complete our picture of how we
|
|
|
|
|
* use RCU.
|
|
|
|
|
*
|
|
|
|
|
* The notification value is in cpu->pending_notify: we return true if it went
|
|
|
|
|
* to an eventfd.
|
|
|
|
|
*/
|
|
|
|
|
bool send_notify_to_eventfd(struct lg_cpu *cpu)
|
|
|
|
|
{
|
|
|
|
|
unsigned int i;
|
|
|
|
|
struct lg_eventfd_map *map;
|
|
|
|
|
|
|
|
|
|
/* We only connect LHCALL_NOTIFY to event fds, not other traps. */
|
|
|
|
|
if (cpu->pending.trap != LGUEST_TRAP_ENTRY)
|
|
|
|
|
return false;
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* This "rcu_read_lock()" helps track when someone is still looking at
|
|
|
|
|
* the (RCU-using) eventfds array. It's not actually a lock at all;
|
|
|
|
|
* indeed it's a noop in many configurations. (You didn't expect me to
|
|
|
|
|
* explain all the RCU secrets here, did you?)
|
|
|
|
|
*/
|
|
|
|
|
rcu_read_lock();
|
|
|
|
|
/*
|
|
|
|
|
* rcu_dereference is the counter-side of rcu_assign_pointer(); it
|
|
|
|
|
* makes sure we don't access the memory pointed to by
|
|
|
|
|
* cpu->lg->eventfds before cpu->lg->eventfds is set. Sounds crazy,
|
|
|
|
|
* but Alpha allows this! Paul McKenney points out that a really
|
|
|
|
|
* aggressive compiler could have the same effect:
|
|
|
|
|
* http://lists.ozlabs.org/pipermail/lguest/2009-July/001560.html
|
|
|
|
|
*
|
|
|
|
|
* So play safe, use rcu_dereference to get the rcu-protected pointer:
|
|
|
|
|
*/
|
|
|
|
|
map = rcu_dereference(cpu->lg->eventfds);
|
|
|
|
|
/*
|
|
|
|
|
* Simple array search: even if they add an eventfd while we do this,
|
|
|
|
|
* we'll continue to use the old array and just won't see the new one.
|
|
|
|
|
*/
|
|
|
|
|
for (i = 0; i < map->num; i++) {
|
|
|
|
|
if (map->map[i].addr == cpu->pending.addr) {
|
|
|
|
|
eventfd_signal(map->map[i].event, 1);
|
|
|
|
|
cpu->pending.trap = 0;
|
|
|
|
|
break;
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
/* We're done with the rcu-protected variable cpu->lg->eventfds. */
|
|
|
|
|
rcu_read_unlock();
|
|
|
|
|
|
|
|
|
|
/* If we cleared the notification, it's because we found a match. */
|
|
|
|
|
return cpu->pending.trap == 0;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/*L:055
|
|
|
|
|
* One of the more tricksy tricks in the Linux Kernel is a technique called
|
|
|
|
|
* Read Copy Update. Since one point of lguest is to teach lguest journeyers
|
|
|
|
|
* about kernel coding, I use it here. (In case you're curious, other purposes
|
|
|
|
|
* include learning about virtualization and instilling a deep appreciation for
|
|
|
|
|
* simplicity and puppies).
|
|
|
|
|
*
|
|
|
|
|
* We keep a simple array which maps LHCALL_NOTIFY values to eventfds, but we
|
|
|
|
|
* add new eventfds without ever blocking readers from accessing the array.
|
|
|
|
|
* The current Launcher only does this during boot, so that never happens. But
|
|
|
|
|
* Read Copy Update is cool, and adding a lock risks damaging even more puppies
|
|
|
|
|
* than this code does.
|
|
|
|
|
*
|
|
|
|
|
* We allocate a brand new one-larger array, copy the old one and add our new
|
|
|
|
|
* element. Then we make the lg eventfd pointer point to the new array.
|
|
|
|
|
* That's the easy part: now we need to free the old one, but we need to make
|
|
|
|
|
* sure no slow CPU somewhere is still looking at it. That's what
|
|
|
|
|
* synchronize_rcu does for us: waits until every CPU has indicated that it has
|
|
|
|
|
* moved on to know it's no longer using the old one.
|
|
|
|
|
*
|
|
|
|
|
* If that's unclear, see http://en.wikipedia.org/wiki/Read-copy-update.
|
|
|
|
|
*/
|
|
|
|
|
static int add_eventfd(struct lguest *lg, unsigned long addr, int fd)
|
|
|
|
|
{
|
|
|
|
|
struct lg_eventfd_map *new, *old = lg->eventfds;
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* We don't allow notifications on value 0 anyway (pending_notify of
|
|
|
|
|
* 0 means "nothing pending").
|
|
|
|
|
*/
|
|
|
|
|
if (!addr)
|
|
|
|
|
return -EINVAL;
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* Replace the old array with the new one, carefully: others can
|
|
|
|
|
* be accessing it at the same time.
|
|
|
|
|
*/
|
|
|
|
|
new = kmalloc(sizeof(*new) + sizeof(new->map[0]) * (old->num + 1),
|
|
|
|
|
GFP_KERNEL);
|
|
|
|
|
if (!new)
|
|
|
|
|
return -ENOMEM;
|
|
|
|
|
|
|
|
|
|
/* First make identical copy. */
|
|
|
|
|
memcpy(new->map, old->map, sizeof(old->map[0]) * old->num);
|
|
|
|
|
new->num = old->num;
|
|
|
|
|
|
|
|
|
|
/* Now append new entry. */
|
|
|
|
|
new->map[new->num].addr = addr;
|
|
|
|
|
new->map[new->num].event = eventfd_ctx_fdget(fd);
|
|
|
|
|
if (IS_ERR(new->map[new->num].event)) {
|
|
|
|
|
int err = PTR_ERR(new->map[new->num].event);
|
|
|
|
|
kfree(new);
|
|
|
|
|
return err;
|
|
|
|
|
}
|
|
|
|
|
new->num++;
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* Now put new one in place: rcu_assign_pointer() is a fancy way of
|
|
|
|
|
* doing "lg->eventfds = new", but it uses memory barriers to make
|
|
|
|
|
* absolutely sure that the contents of "new" written above is nailed
|
|
|
|
|
* down before we actually do the assignment.
|
|
|
|
|
*
|
|
|
|
|
* We have to think about these kinds of things when we're operating on
|
|
|
|
|
* live data without locks.
|
|
|
|
|
*/
|
|
|
|
|
rcu_assign_pointer(lg->eventfds, new);
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* We're not in a big hurry. Wait until no one's looking at old
|
|
|
|
|
* version, then free it.
|
|
|
|
|
*/
|
|
|
|
|
synchronize_rcu();
|
|
|
|
|
kfree(old);
|
|
|
|
|
|
|
|
|
|
return 0;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/*L:052
|
|
|
|
|
* Receiving notifications from the Guest is usually done by attaching a
|
|
|
|
|
* particular LHCALL_NOTIFY value to an event filedescriptor. The eventfd will
|
|
|
|
|
* become readable when the Guest does an LHCALL_NOTIFY with that value.
|
|
|
|
|
*
|
|
|
|
|
* This is really convenient for processing each virtqueue in a separate
|
|
|
|
|
* thread.
|
|
|
|
|
*/
|
|
|
|
|
static int attach_eventfd(struct lguest *lg, const unsigned long __user *input)
|
|
|
|
|
{
|
|
|
|
|
unsigned long addr, fd;
|
|
|
|
|
int err;
|
|
|
|
|
|
|
|
|
|
if (get_user(addr, input) != 0)
|
|
|
|
|
return -EFAULT;
|
|
|
|
|
input++;
|
|
|
|
|
if (get_user(fd, input) != 0)
|
|
|
|
|
return -EFAULT;
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* Just make sure two callers don't add eventfds at once. We really
|
|
|
|
|
* only need to lock against callers adding to the same Guest, so using
|
|
|
|
|
* the Big Lguest Lock is overkill. But this is setup, not a fast path.
|
|
|
|
|
*/
|
|
|
|
|
mutex_lock(&lguest_lock);
|
|
|
|
|
err = add_eventfd(lg, addr, fd);
|
|
|
|
|
mutex_unlock(&lguest_lock);
|
|
|
|
|
|
|
|
|
|
return err;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/* The Launcher can get the registers, and also set some of them. */
|
|
|
|
|
The Launcher can get the registers, and also set some of them.
|
|
|
|
|
*/
|
|
|
|
|
static int getreg_setup(struct lg_cpu *cpu, const unsigned long __user *input)
|
|
|
|
|
{
|
|
|
|
|
unsigned long which;
|
|
|
|
|
@ -409,13 +247,6 @@ static int initialize(struct file *file, const unsigned long __user *input)
|
|
|
|
|
goto unlock;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
lg->eventfds = kmalloc(sizeof(*lg->eventfds), GFP_KERNEL);
|
|
|
|
|
if (!lg->eventfds) {
|
|
|
|
|
err = -ENOMEM;
|
|
|
|
|
goto free_lg;
|
|
|
|
|
}
|
|
|
|
|
lg->eventfds->num = 0;
|
|
|
|
|
|
|
|
|
|
/* Populate the easy fields of our "struct lguest" */
|
|
|
|
|
lg->mem_base = (void __user *)args[0];
|
|
|
|
|
lg->pfn_limit = args[1];
|
|
|
|
|
@ -424,7 +255,7 @@ static int initialize(struct file *file, const unsigned long __user *input)
|
|
|
|
|
/* This is the first cpu (cpu 0) and it will start booting at args[2] */
|
|
|
|
|
err = lg_cpu_start(&lg->cpus[0], 0, args[2]);
|
|
|
|
|
if (err)
|
|
|
|
|
goto free_eventfds;
|
|
|
|
|
goto free_lg;
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* Initialize the Guest's shadow page tables. This allocates
|
|
|
|
|
@ -445,8 +276,6 @@ static int initialize(struct file *file, const unsigned long __user *input)
|
|
|
|
|
free_regs:
|
|
|
|
|
/* FIXME: This should be in free_vcpu */
|
|
|
|
|
free_page(lg->cpus[0].regs_page);
|
|
|
|
|
free_eventfds:
|
|
|
|
|
kfree(lg->eventfds);
|
|
|
|
|
free_lg:
|
|
|
|
|
kfree(lg);
|
|
|
|
|
unlock:
|
|
|
|
|
@ -499,8 +328,6 @@ static ssize_t write(struct file *file, const char __user *in,
|
|
|
|
|
return initialize(file, input);
|
|
|
|
|
case LHREQ_IRQ:
|
|
|
|
|
return user_send_irq(cpu, input);
|
|
|
|
|
case LHREQ_EVENTFD:
|
|
|
|
|
return attach_eventfd(lg, input);
|
|
|
|
|
case LHREQ_GETREG:
|
|
|
|
|
return getreg_setup(cpu, input);
|
|
|
|
|
case LHREQ_SETREG:
|
|
|
|
|
@ -551,11 +378,6 @@ static int close(struct inode *inode, struct file *file)
|
|
|
|
|
mmput(lg->cpus[i].mm);
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/* Release any eventfds they registered. */
|
|
|
|
|
for (i = 0; i < lg->eventfds->num; i++)
|
|
|
|
|
eventfd_ctx_put(lg->eventfds->map[i].event);
|
|
|
|
|
kfree(lg->eventfds);
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* If lg->dead doesn't contain an error code it will be NULL or a
|
|
|
|
|
* kmalloc()ed string, either of which is ok to hand to kfree().
|
|
|
|
|
|
Rusty Russell