Introduce "hcall" pointer to indicate pending hypercall.
Currently we look at the "trapnum" to see if the Guest wants a
hypercall. But once the hypercall is done we have to reset trapnum to
a bogus value, otherwise if we exit to userspace and return, we'd run
the same hypercall twice (that was a nasty bug to find!).
This has two main effects:
1) When Jes's patch changes the hypercall args to be a generic "struct
hcall_args" we simply change the type of "lg->hcall". It's set by
arch code, so if it has to copy args or something it can do so, and
point "hcall" into lg->arch somewhere.
2) Async hypercalls only get run when an actual hypercall is pending.
This simplfies the code a little and is a more logical semantic.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c
index 06869a2..02556ba 100644
--- a/drivers/lguest/core.c
+++ b/drivers/lguest/core.c
@@ -198,10 +198,10 @@
{
/* We stop running once the Guest is dead. */
while (!lg->dead) {
- /* First we run any hypercalls the Guest wants done: either in
- * the hypercall ring in "struct lguest_data", or directly by
- * using int 31 (LGUEST_TRAP_ENTRY). */
- do_hypercalls(lg);
+ /* First we run any hypercalls the Guest wants done. */
+ if (lg->hcall)
+ do_hypercalls(lg);
+
/* It's possible the Guest did a SEND_DMA hypercall to the
* Launcher, in which case we return from the read() now. */
if (lg->dma_is_pending) {