On Wed, Jul 04, 2007 at 04:20:33PM +1000, Rusty Russell wrote:
> We create an "lguest_clock" which the guest uses: either TSC or
> jiffies, depending on whether the host tells us the TSC frequency.
>
> Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
> ---
> drivers/lguest/lguest.c | 51 +++++++++++++++++++++++------------------------
> 1 file changed, 26 insertions(+), 25 deletions(-)
>
> ===================================================================
Hi Rusty,
<snip>
> +static cycle_t lguest_clock_read(void)
> +{
> + if (lguest_data.tsc_khz)
> + return native_read_tsc();
> + else
> + return jiffies;
> +}
> +
> +/* This is what we tell the kernel is our clocksource. */
<snip>
> + /* We use the TSC if the Host tells us we can, otherwise a dumb
> + * jiffies-based clock. */
> + if (lguest_data.tsc_khz) {
> + lguest_clock.shift = 22;
> + lguest_clock.mult = clocksource_khz2mult(lguest_data.tsc_khz,
> + lguest_clock.shift);
> + lguest_clock.mask = CLOCKSOURCE_MASK(64);
> + lguest_clock.flags = CLOCK_SOURCE_IS_CONTINUOUS;
> + } else {
> + /* To understand this, start at kernel/time/jiffies.c... */
> + lguest_clock.shift = 8;
> + lguest_clock.mult = (((u64)NSEC_PER_SEC<<8)/ACTHZ) << 8;
> + lguest_clock.mask = CLOCKSOURCE_MASK(32);
> + }
> clocksource_register(&lguest_clock);
Why bother installing an lguest_clock which is the same as jiffies?
Wouldn't it be better to just use the system provided jiffies
clocksource in the case where you haven't been provided with
lguest_data.tsc_khz ?
Yours Tony
linux.conf.au http://linux.conf.au/ || http://lca2008.linux.org.au/
Jan 28 - Feb 02 2008 The Australian Linux Technical Conference!
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