Provide timespec to guests rather than jiffies clock.

A non-periodic clock_event_device and the "jiffies" clock don't mix well:
tick_handle_periodic() can go into an infinite loop.

Currently lguest guests use the jiffies clock when the TSC is
unusable.  Instead, make the Host write the current time into the lguest
page on every interrupt.  This doesn't cost much but is more precise
and at least as accurate as the jiffies clock.  It also gets rid of
the GET_WALLCLOCK hypercall.

Also, delay setting sched_clock until our clock is set up, otherwise
the early printk timestamps can go backwards (not harmful, just ugly).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/lguest/lg.h b/drivers/lguest/lg.h
index 269116eee85f..64f0abed317c 100644
--- a/drivers/lguest/lg.h
+++ b/drivers/lguest/lg.h
@@ -256,6 +256,7 @@ unsigned long get_dma_buffer(struct lguest *lg, unsigned long key,
 
 /* hypercalls.c: */
 void do_hypercalls(struct lguest *lg);
+void write_timestamp(struct lguest *lg);
 
 /*L:035
  * Let's step aside for the moment, to study one important routine that's used