lguest: update commentry

Every so often, after code shuffles, I need to go through and unbitrot
the Lguest Journey (see drivers/lguest/README).  Since we now use RCU in
a simple form in one place I took the opportunity to expand that explanation.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c
index cd058bc903ff..1e2cb846b3c9 100644
--- a/drivers/lguest/core.c
+++ b/drivers/lguest/core.c
@@ -217,10 +217,15 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user)
 
                 /*
                  * It's possible the Guest did a NOTIFY hypercall to the
-                 * Launcher, in which case we return from the read() now.
+                 * Launcher.
                  */
                 if (cpu->pending_notify) {
+                        /*
+                         * Does it just needs to write to a registered
+                         * eventfd (ie. the appropriate virtqueue thread)?
+                         */
                         if (!send_notify_to_eventfd(cpu)) {
+                                /* OK, we tell the main Laucher. */
                                 if (put_user(cpu->pending_notify, user))
                                         return -EFAULT;
                                 return sizeof(cpu->pending_notify);