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From: Michael Kelley <mikelley@microsoft.com>
To: Juergen Gross <jgross@suse.com>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
	"x86@kernel.org" <x86@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
	"virtualization@lists.linux-foundation.org" 
	<virtualization@lists.linux-foundation.org>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	KY Srinivasan <kys@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	Wei Liu <wei.liu@kernel.org>, Deep Shah <sdeep@vmware.com>,
	"VMware, Inc." <pv-drivers@vmware.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <seanjc@google.com>,
	vkuznets <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Daniel Lezcano <daniel.lezcano@linaro.org>
Subject: RE: [PATCH v4 07/15] x86/paravirt: switch time pvops functions to use static_call()
Date: Sun, 24 Jan 2021 16:14:52 +0000	[thread overview]
Message-ID: <MWHPR21MB15930A0BC65D8A3F31C13F49D7BE9@MWHPR21MB1593.namprd21.prod.outlook.com> (raw)
In-Reply-To: <20210120135555.32594-8-jgross@suse.com>

From: Juergen Gross <jgross@suse.com> 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@suse.com>
> ---
> 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

  reply	other threads:[~2021-01-24 16:15 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-20 13:55 [PATCH v4 00/15] x86: major paravirt cleanup Juergen Gross
2021-01-20 13:55 ` [PATCH v4 07/15] x86/paravirt: switch time pvops functions to use static_call() Juergen Gross
2021-01-24 16:14   ` Michael Kelley [this message]
2021-02-01 19:48   ` Borislav Petkov
  -- strict thread matches above, loose matches on Subject: below --
2021-01-20 13:25 [PATCH v4 00/15] x86: major paravirt cleanup Juergen Gross
2021-01-20 13:26 ` [PATCH v4 07/15] x86/paravirt: switch time pvops functions to use static_call() Juergen Gross

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