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Commit 37250097 authored by Rusty Russell's avatar Rusty Russell Committed by Linus Torvalds
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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: default avatarRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 88ffc350

drivers/lguest/lguest.c

+2 −2
Original line number Diff line number Diff line
@@ -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;