lguest: make write() operation smp aware

This patch makes the write() file operation smp aware. Which means, receiving
the vcpu_id value through the offset parameter, and being well aware to which
vcpu we're talking to.

Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 9 insertions, 2 deletions

diff --git a/drivers/lguest/lguest_user.c b/drivers/lguest/lguest_user.c
index 9f0a44329947..2562082a3ea3 100644
--- a/drivers/lguest/lguest_user.c
+++ b/drivers/lguest/lguest_user.c
@@ -227,14 +227,21 @@ static ssize_t write(struct file *file, const char __user *in,
         struct lguest *lg = file->private_data;
         const unsigned long __user *input = (const unsigned long __user *)in;
         unsigned long req;
+        struct lg_cpu *cpu;
+        unsigned int cpu_id = *off;
 
         if (get_user(req, input) != 0)
                 return -EFAULT;
         input++;
 
         /* If you haven't initialized, you must do that first. */
-        if (req != LHREQ_INITIALIZE && !lg)
-                return -EINVAL;
+        if (req != LHREQ_INITIALIZE) {
+                if (!lg || (cpu_id >= lg->nr_cpus))
+                        return -EINVAL;
+                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)