RE: [PATCH 2/7] clocksource/drivers: Suspend/resume Hyper-V clocksource for hibernation

Michael Kelley
2019-07-30T22:24:07Z

From: Dexuan Cui <decui@microsoft.com> Sent: Monday, July 8, 2019 10:29 PM
>
> This is needed for hibernation, e.g. when we resume the old kernel, we need
> to disable the "current" kernel's TSC page and then resume the old kernel's.
>
> Signed-off-by: Dexuan Cui <decui@microsoft.com>
> ---
> drivers/clocksource/hyperv_timer.c | 25 +++++++++++++++++++++++++
> 1 file changed, 25 insertions(+)
>
> diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
> index ba2c79e6..41c31a7 100644
> --- a/drivers/clocksource/hyperv_timer.c
> +++ b/drivers/clocksource/hyperv_timer.c
> @@ -237,12 +237,37 @@ static u64 read_hv_clock_tsc(struct clocksource *arg)
> return read_hv_sched_clock_tsc();
> }
>
> +static void suspend_hv_clock_tsc(struct clocksource *arg)
> +{
> + u64 tsc_msr;
> +
> + /* Disable the TSC page */
> + hv_get_reference_tsc(tsc_msr);
> + tsc_msr &= ~BIT_ULL(0);
> + hv_set_reference_tsc(tsc_msr);
> +}
> +
> +
> +static void resume_hv_clock_tsc(struct clocksource *arg)
> +{
> + phys_addr_t phys_addr = page_to_phys(vmalloc_to_page(tsc_pg));
> + u64 tsc_msr;
> +
> + /* Re-enable the TSC page */
> + hv_get_reference_tsc(tsc_msr);
> + tsc_msr &= GENMASK_ULL(11, 0);
> + tsc_msr |= BIT_ULL(0) | (u64)phys_addr;
> + hv_set_reference_tsc(tsc_msr);
> +}
> +
> static struct clocksource hyperv_cs_tsc = {
> .name = "hyperv_clocksource_tsc_page",
> .rating = 400,
> .read = read_hv_clock_tsc,
> .mask = CLOCKSOURCE_MASK(64),
> .flags = CLOCK_SOURCE_IS_CONTINUOUS,
> + .suspend= suspend_hv_clock_tsc,
> + .resume = resume_hv_clock_tsc,
> };
> #endif
>
> --
> 1.8.3.1

Reviewed-by: Michael Kelley <mikelley@microsoft.com>