From: Juergen Gross <jgross@xxxxxxxx> Sent: Wednesday, January 20, 2021 5:56 AM
>
> The time pvops functions are the only ones left which might be
> used in 32-bit mode and which return a 64-bit value.
>
> Switch them to use the static_call() mechanism instead of pvops, as
> this allows quite some simplification of the pvops implementation.
>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> ---
> V4:
> - drop paravirt_time.h again
> - don't move Hyper-V code (Michael Kelley)
> ---
> arch/x86/Kconfig | 1 +
> arch/x86/include/asm/mshyperv.h | 2 +-
> arch/x86/include/asm/paravirt.h | 17 ++++++++++++++---
> arch/x86/include/asm/paravirt_types.h | 6 ------
> arch/x86/kernel/cpu/vmware.c | 5 +++--
> arch/x86/kernel/kvm.c | 2 +-
> arch/x86/kernel/kvmclock.c | 2 +-
> arch/x86/kernel/paravirt.c | 16 ++++++++++++----
> arch/x86/kernel/tsc.c | 2 +-
> arch/x86/xen/time.c | 11 ++++-------
> drivers/clocksource/hyperv_timer.c | 5 +++--
> drivers/xen/time.c | 2 +-
> 12 files changed, 42 insertions(+), 29 deletions(-)
>
[snip]
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index 30f76b966857..b4ee331d29a7 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -63,7 +63,7 @@ typedef int (*hyperv_fill_flush_list_func)(
> static __always_inline void hv_setup_sched_clock(void *sched_clock)
> {
> #ifdef CONFIG_PARAVIRT
> - pv_ops.time.sched_clock = sched_clock;
> + paravirt_set_sched_clock(sched_clock);
> #endif
> }
>
This looks fine.
[snip]
> diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
> index ba04cb381cd3..bf3bf20bc6bd 100644
> --- a/drivers/clocksource/hyperv_timer.c
> +++ b/drivers/clocksource/hyperv_timer.c
> @@ -18,6 +18,7 @@
> #include <linux/sched_clock.h>
> #include <linux/mm.h>
> #include <linux/cpuhotplug.h>
> +#include <linux/static_call.h>
> #include <clocksource/hyperv_timer.h>
> #include <asm/hyperv-tlfs.h>
> #include <asm/mshyperv.h>
> @@ -445,7 +446,7 @@ static bool __init hv_init_tsc_clocksource(void)
> clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
>
> hv_sched_clock_offset = hv_read_reference_counter();
> - hv_setup_sched_clock(read_hv_sched_clock_tsc);
> + paravirt_set_sched_clock(read_hv_sched_clock_tsc);
>
> return true;
> }
> @@ -470,6 +471,6 @@ void __init hv_init_clocksource(void)
> clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
>
> hv_sched_clock_offset = hv_read_reference_counter();
> - hv_setup_sched_clock(read_hv_sched_clock_msr);
> + static_call_update(pv_sched_clock, read_hv_sched_clock_msr);
> }
> EXPORT_SYMBOL_GPL(hv_init_clocksource);
The changes to hyperv_timer.c aren't needed and shouldn't be
there, so as to preserve hyperv_timer.c as architecture neutral. With
your update to hv_setup_sched_clock() in mshyperv.h, the original
code works correctly. While there are two call sites for
hv_setup_sched_clock(), only one is called. And once the sched clock
function is set, it is never changed or overridden.
Michael
