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

["Jürgen Groß" <jgross@suse.com>]

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On 17.12.20 18:31, Michael Kelley wrote:
> From: Juergen Gross <jgross@suse.com> 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@suse.com>
>> ---
>>   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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