2023-04-08 21:15:48

by Dexuan Cui

Subject: [PATCH] clocksource: hyper-v: make sure Invariant-TSC is used if it is available

If Hyper-V TSC page is unavailable and Invariant-TSC is available,
currently hyperv_cs_msr (rather than Invariant-TSC) is used by default.

Use Invariant-TSC by default by downgrading hyperv_cs_msr.rating in
hv_init_tsc_clocksource(), if Invariant-TSC is available.

Signed-off-by: Dexuan Cui <[email protected]>
---
drivers/clocksource/hyperv_timer.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index c0cef92b12b82..7901a88ad9188 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -506,9 +506,6 @@ static bool __init hv_init_tsc_clocksource(void)
{
union hv_reference_tsc_msr tsc_msr;

- if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
- return false;
-
/*
* If Hyper-V offers TSC_INVARIANT, then the virtualized TSC correctly
* handles frequency and offset changes due to live migration,
@@ -525,6 +522,9 @@ static bool __init hv_init_tsc_clocksource(void)
hyperv_cs_msr.rating = 250;
}

+ if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
+ return false;
+
hv_read_reference_counter = read_hv_clock_tsc;

/*
--
2.25.1

2023-04-11 17:32:40

by Michael Kelley (LINUX)

Subject: RE: [PATCH] clocksource: hyper-v: make sure Invariant-TSC is used if it is available

From: Dexuan Cui <[email protected]> Sent: Saturday, April 8, 2023 2:04 PM
>
> If Hyper-V TSC page is unavailable and Invariant-TSC is available,
> currently hyperv_cs_msr (rather than Invariant-TSC) is used by default.
>
> Use Invariant-TSC by default by downgrading hyperv_cs_msr.rating in
> hv_init_tsc_clocksource(), if Invariant-TSC is available.
>
> Signed-off-by: Dexuan Cui <[email protected]>
> ---
> drivers/clocksource/hyperv_timer.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
> index c0cef92b12b82..7901a88ad9188 100644
> --- a/drivers/clocksource/hyperv_timer.c
> +++ b/drivers/clocksource/hyperv_timer.c
> @@ -506,9 +506,6 @@ static bool __init hv_init_tsc_clocksource(void)
> {
> union hv_reference_tsc_msr tsc_msr;
>
> - if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
> - return false;
> -
> /*
> * If Hyper-V offers TSC_INVARIANT, then the virtualized TSC correctly
> * handles frequency and offset changes due to live migration,
> @@ -525,6 +522,9 @@ static bool __init hv_init_tsc_clocksource(void)
> hyperv_cs_msr.rating = 250;
> }
>
> + if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
> + return false;
> +
> hv_read_reference_counter = read_hv_clock_tsc;
>
> /*
> --
> 2.25.1

Reviewed-by: Michael Kelley <[email protected]>

2023-04-13 01:19:20

by Wei Liu

Subject: Re: [PATCH] clocksource: hyper-v: make sure Invariant-TSC is used if it is available

On Tue, Apr 11, 2023 at 05:28:39PM +0000, Michael Kelley (LINUX) wrote:
> From: Dexuan Cui <[email protected]> Sent: Saturday, April 8, 2023 2:04 PM
> Reviewed-by: Michael Kelley <[email protected]>
>

Applied to hyperv-next. Thanks.