diff options
Diffstat (limited to 'drivers/lguest/lguest_user.c')
| -rw-r--r-- | drivers/lguest/lguest_user.c | 32 |
1 files changed, 22 insertions, 10 deletions
diff --git a/drivers/lguest/lguest_user.c b/drivers/lguest/lguest_user.c index 2221485b077..645e6e040bf 100644 --- a/drivers/lguest/lguest_user.c +++ b/drivers/lguest/lguest_user.c @@ -73,7 +73,7 @@ static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o) 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; @@ -88,7 +88,7 @@ static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o) 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 (cpu->pending_notify) cpu->pending_notify = 0; @@ -97,14 +97,20 @@ static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o) 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 @@ -120,11 +126,11 @@ static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip) * 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 @@ -136,6 +142,7 @@ static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip) * when the same Guest runs on the same CPU twice. */ cpu->last_pages = NULL; + /* No error == success. */ return 0; } @@ -182,17 +189,16 @@ static int initialize(struct file *file, const unsigned long __user *input) } /* 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; @@ -218,11 +224,16 @@ unlock: /*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; @@ -230,6 +241,7 @@ static ssize_t write(struct file *file, const char __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++; |