Re: [PATCH v3 06/15] x86/paravirt: switch time pvops functions to use static_call()

[Jürgen Groß <jgross@xxxxxxxx>]

On 17.12.20 18:31, Michael Kelley wrote:
> From: Juergen Gross <jgross@xxxxxxxx> Sent: Thursday, December 17, 2020 1:31 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.
> >
> > Due to include hell this requires to split out the time interfaces
> > into a new header file.
> >
> > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> > ---
> >   arch/x86/Kconfig                      |  1 +
> >   arch/x86/include/asm/mshyperv.h       | 11 --------
> >   arch/x86/include/asm/paravirt.h       | 14 ----------
> >   arch/x86/include/asm/paravirt_time.h  | 38 +++++++++++++++++++++++++++
> >   arch/x86/include/asm/paravirt_types.h |  6 -----
> >   arch/x86/kernel/cpu/vmware.c          |  5 ++--
> >   arch/x86/kernel/kvm.c                 |  3 ++-
> >   arch/x86/kernel/kvmclock.c            |  3 ++-
> >   arch/x86/kernel/paravirt.c            | 16 ++++++++---
> >   arch/x86/kernel/tsc.c                 |  3 ++-
> >   arch/x86/xen/time.c                   | 12 ++++-----
> >   drivers/clocksource/hyperv_timer.c    |  5 ++--
> >   drivers/xen/time.c                    |  3 ++-
> >   kernel/sched/sched.h                  |  1 +
> >   14 files changed, 71 insertions(+), 50 deletions(-)
> >   create mode 100644 arch/x86/include/asm/paravirt_time.h
> [snip]
>   
> > diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> > index ffc289992d1b..45942d420626 100644
> > --- a/arch/x86/include/asm/mshyperv.h
> > +++ b/arch/x86/include/asm/mshyperv.h
> > @@ -56,17 +56,6 @@ typedef int (*hyperv_fill_flush_list_func)(
> >   #define hv_get_raw_timer() rdtsc_ordered()
> >   #define hv_get_vector() HYPERVISOR_CALLBACK_VECTOR
> >
> > -/*
> > - * Reference to pv_ops must be inline so objtool
> > - * detection of noinstr violations can work correctly.
> > - */
> > -static __always_inline void hv_setup_sched_clock(void *sched_clock)
> > -{
> > -#ifdef CONFIG_PARAVIRT
> > -       pv_ops.time.sched_clock = sched_clock;
> > -#endif
> > -}
> > -
> >   void hyperv_vector_handler(struct pt_regs *regs);
> >
> >   static inline void hv_enable_stimer0_percpu_irq(int irq) {}
> [snip]
>
> > diff --git a/drivers/clocksource/hyperv_timer.c 
> > b/drivers/clocksource/hyperv_timer.c
> > index ba04cb381cd3..1ed79993fc50 100644
> > --- a/drivers/clocksource/hyperv_timer.c
> > +++ b/drivers/clocksource/hyperv_timer.c
> > @@ -21,6 +21,7 @@
> >   #include <clocksource/hyperv_timer.h>
> >   #include <asm/hyperv-tlfs.h>
> >   #include <asm/mshyperv.h>
> > +#include <asm/paravirt_time.h>
> >
> >   static struct clock_event_device __percpu *hv_clock_event;
> >   static u64 hv_sched_clock_offset __ro_after_init;
> > @@ -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);
> These Hyper-V changes are problematic as we want to keep hyperv_timer.c
> architecture independent.  While only the code for x86/x64 is currently
> accepted upstream, code for ARM64 support is in progress.   So we need
> to use hv_setup_sched_clock() in hyperv_timer.c, and have the per-arch
> implementation in mshyperv.h.
Okay, will switch back to old setup.


Juergen

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