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>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/lguest/lg.h b/drivers/lguest/lg.h
index 203d3100c3b4..662994b776cc 100644
--- a/drivers/lguest/lg.h
+++ b/drivers/lguest/lg.h
@@ -106,6 +106,9 @@ struct lguest
 	u32 esp1;
 	u8 ss1;
 
+	/* If a hypercall was asked for, this points to the arguments. */
+	struct lguest_regs *hcall;
+
 	/* Do we need to stop what we're doing and return to userspace? */
 	int break_out;
 	wait_queue_head_t break_wq;