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/x86/core.c b/drivers/lguest/x86/core.c
index e2f46b1..0cc251c 100644
--- a/drivers/lguest/x86/core.c
+++ b/drivers/lguest/x86/core.c
@@ -316,13 +316,14 @@
return;
break;
case 32 ... 255:
- /* These values mean a real interrupt occurred, in
- * which case the Host handler has already been run.
- * We just do a friendly check if another process
- * should now be run, then fall through to loop
- * around: */
+ /* These values mean a real interrupt occurred, in which case
+ * the Host handler has already been run. We just do a
+ * friendly check if another process should now be run, then
+ * return to run the Guest again */
cond_resched();
- case LGUEST_TRAP_ENTRY: /* Handled before re-entering Guest */
+ return;
+ case LGUEST_TRAP_ENTRY:
+ lg->hcall = lg->regs;
return;
}