Fix non-TSC guest clocksource lockup

lguest uses a host-supplied wallclock-based clocksource when the TSC
is not reliable.  As this is already in nanoseconds, I naively used a
multiplier of 1 and a shift of 0.

But update_wall_time() in its infinite wisdom decides to adjust the
clock a little (where does it think it's getting a more accurate time
from?)

It will happily tweak the multiplier... to 0, then -1.

So the "fix" is to use a shift of 22 like everyone else, and a
multiplier of 1 << 22.

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

diff --git a/drivers/lguest/lguest.c b/drivers/lguest/lguest.c
index 1bc1546..fb17d27 100644 (file)
--- a/drivers/lguest/lguest.c
+++ b/drivers/lguest/lguest.c
@@ -687,7 +687,8 @@ static struct clocksource lguest_clock = {
        .rating         = 400,
        .read           = lguest_clock_read,
        .mask           = CLOCKSOURCE_MASK(64),
-       .mult           = 1,
+       .mult           = 1 << 22,
+       .shift          = 22,
 };
 
 /* The "scheduler clock" is just our real clock, adjusted to start at zero */
@@ -770,7 +771,6 @@ static void lguest_time_init(void)
         * way, the "rating" is initialized so high that it's always chosen
         * over any other clocksource. */
        if (lguest_data.tsc_khz) {
-               lguest_clock.shift = 22;
                lguest_clock.mult = clocksource_khz2mult(lguest_data.tsc_khz,
                                                         lguest_clock.shift);
                lguest_clock.flags = CLOCK_SOURCE_IS_CONTINUOUS;