#include <linux/uaccess.h>
#include <linux/miscdevice.h>
#include <linux/fs.h>
+#include <linux/sched.h>
#include "lg.h"
/*L:055 When something happens, the Waker process needs a way to stop the
if (current != cpu->tsk)
return -EPERM;
- /* If the guest is already dead, we indicate why */
+ /* If the Guest is already dead, we indicate why */
if (lg->dead) {
size_t len;
return len;
}
- /* If we returned from read() last time because the Guest notified,
+ /* If we returned from read() last time because the Guest sent I/O,
* clear the flag. */
- if (lg->pending_notify)
- lg->pending_notify = 0;
+ if (cpu->pending_notify)
+ cpu->pending_notify = 0;
/* Run the Guest until something interesting happens. */
return run_guest(cpu, (unsigned long __user *)user);
}
+/*L:025 This actually initializes a CPU. For the moment, a Guest is only
+ * uniprocessor, so "id" is always 0. */
static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip)
{
+ /* We have a limited number the number of CPUs in the lguest struct. */
if (id >= NR_CPUS)
return -EINVAL;
+ /* Set up this CPU's id, and pointer back to the lguest struct. */
cpu->id = id;
cpu->lg = container_of((cpu - id), struct lguest, cpus[0]);
cpu->lg->nr_cpus++;
+
+ /* Each CPU has a timer it can set. */
init_clockdev(cpu);
/* We need a complete page for the Guest registers: they are accessible
* address. */
lguest_arch_setup_regs(cpu, start_ip);
- /* Initialize the queue for the waker to wait on */
+ /* Initialize the queue for the Waker to wait on */
init_waitqueue_head(&cpu->break_wq);
/* We keep a pointer to the Launcher task (ie. current task) for when
- * other Guests want to wake this one (inter-Guest I/O). */
+ * other Guests want to wake this one (eg. console input). */
cpu->tsk = current;
/* We need to keep a pointer to the Launcher's memory map, because if
* reference, it is destroyed before close() is called. */
cpu->mm = get_task_mm(cpu->tsk);
+ /* We remember which CPU's pages this Guest used last, for optimization
+ * when the same Guest runs on the same CPU twice. */
+ cpu->last_pages = NULL;
+
+ /* No error == success. */
return 0;
}
}
/* Populate the easy fields of our "struct lguest" */
- lg->mem_base = (void __user *)(long)args[0];
+ lg->mem_base = (void __user *)args[0];
lg->pfn_limit = args[1];
- /* This is the first cpu */
+ /* This is the first cpu (cpu 0) and it will start booting at args[3] */
err = lg_cpu_start(&lg->cpus[0], 0, args[3]);
if (err)
goto release_guest;
/* Initialize the Guest's shadow page tables, using the toplevel
- * address the Launcher gave us. This allocates memory, so can
- * fail. */
+ * address the Launcher gave us. This allocates memory, so can fail. */
err = init_guest_pagetable(lg, args[2]);
if (err)
goto free_regs;
- /* We remember which CPU's pages this Guest used last, for optimization
- * when the same Guest runs on the same CPU twice. */
- lg->last_pages = NULL;
-
/* We keep our "struct lguest" in the file's private_data. */
file->private_data = lg;
/*L:010 The first operation the Launcher does must be a write. All writes
* start with an unsigned long number: for the first write this must be
* LHREQ_INITIALIZE to set up the Guest. After that the Launcher can use
- * writes of other values to send interrupts. */
+ * writes of other values to send interrupts.
+ *
+ * Note that we overload the "offset" in the /dev/lguest file to indicate what
+ * CPU number we're dealing with. Currently this is always 0, since we only
+ * support uniprocessor Guests, but you can see the beginnings of SMP support
+ * here. */
static ssize_t write(struct file *file, const char __user *in,
size_t size, loff_t *off)
{
- /* Once the guest is initialized, we hold the "struct lguest" in the
+ /* Once the Guest is initialized, we hold the "struct lguest" in the
* file private data. */
struct lguest *lg = file->private_data;
const unsigned long __user *input = (const unsigned long __user *)in;
struct lg_cpu *uninitialized_var(cpu);
unsigned int cpu_id = *off;
+ /* The first value tells us what this request is. */
if (get_user(req, input) != 0)
return -EFAULT;
input++;
cpu = &lg->cpus[cpu_id];
if (!cpu)
return -EINVAL;
- }
- /* Once the Guest is dead, all you can do is read() why it died. */
- if (lg && lg->dead)
- return -ENOENT;
+ /* Once the Guest is dead, you can only read() why it died. */
+ if (lg->dead)
+ return -ENOENT;
- /* If you're not the task which owns the Guest, you can only break */
- if (lg && current != cpu->tsk && req != LHREQ_BREAK)
- return -EPERM;
+ /* If you're not the task which owns the Guest, all you can do
+ * is break the Launcher out of running the Guest. */
+ if (current != cpu->tsk && req != LHREQ_BREAK)
+ return -EPERM;
+ }
switch (req) {
case LHREQ_INITIALIZE: