Re: [PATCH v4 07/15] x86/paravirt: switch time pvops functions to use static_call()
On Wed, Jan 20, 2021 at 02:55:47PM +0100, Juergen Gross wrote:
> 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
> ---
> 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(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 21f851179ff0..7ccd4a80788c 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -771,6 +771,7 @@ if HYPERVISOR_GUEST
>
> config PARAVIRT
> bool "Enable paravirtualization code"
> + depends on HAVE_STATIC_CALL
> help
> This changes the kernel so it can modify itself when it is run
> under a hypervisor, potentially improving performance significantly
> 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
> }
>
> diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
> index 4abf110e2243..1e45b46fae84 100644
> --- a/arch/x86/include/asm/paravirt.h
> +++ b/arch/x86/include/asm/paravirt.h
> @@ -15,11 +15,22 @@
> #include
> #include
> #include
> +#include
> #include
>
> -static inline unsigned long long paravirt_sched_clock(void)
> +u64 dummy_steal_clock(int cpu);
> +u64 dummy_sched_clock(void);
> +
> +DECLARE_STATIC_CALL(pv_steal_clock, dummy_steal_clock);
> +DECLARE_STATIC_CALL(pv_sched_clock, dummy_sched_clock);
Did you build this before sending?
I'm test-applying this on rc6 + tip/master so I probably am using a
different tree so it looks like something has changed in the meantime.
-rc6 has a couple of Xen changes which made applying those to need some
wiggling in...
Maybe you should redo them ontop of tip/master. That is, *if* they're
going to eventually go through tip. The diffstat has Xen stuff too so we
might need some synchronization here what goes where how...
./arch/x86/include/asm/paravirt.h:24:1: warning: data definition has no type or
storage class
24 | DECLARE_STATIC_CALL(pv_steal_clock, dummy_steal_clock);
| ^~~
./arch/x86/include/asm/paravirt.h:24:1: error: type defaults to ‘int’ in
declaration of ‘DECLARE_STATIC_CALL’ [-Werror=implicit-int]
./arch/x86/include/asm/paravirt.h:24:1: warning: parameter names (without
types) in function declaration
./arch/x86/include/asm/paravirt.h:25:1: warning: data definition has no type or
storage class
25 | DECLARE_STATIC_CALL(pv_sched_clock, dummy_sched_clock);
| ^~~
./arch/x86/include/asm/paravirt.h:25:1: error: type defaults to ‘int’ in
declaration of ‘DECLARE_STATIC_CALL’ [-Werror=implicit-int]
./arch/x86/include/asm/paravirt.h:25:1: warning: parameter names (without
types) in function declaration
./arch/x86/include/asm/paravirt.h: In function ‘paravirt_sched_clock’:
./arch/x86/include/asm/paravirt.h:33:9: error: implicit declaration of function
‘static_call’ [-Werror=implicit-function-declaration]
33 | return static_call(pv_sched_clock)();
| ^~~
./arch/x86/include/asm/paravirt.h:33:21: error: ‘pv_sched_clock’ undeclared
(first use in this function); did you mean ‘dummy_sched_clock’?
33 | return static_call(pv_sched_clock)();
| ^~
| dummy_sched_clock
./arch/x86/include/asm/paravirt.h:33:21: note: each undeclared identifier is
reported only once for each function it appears in
./arch/x86/include/asm/paravirt.h: In function ‘paravirt_steal_clock’:
./arch/x86/include/asm/paravirt.h:47:21: error: ‘pv_steal_clock’ undeclared
(first use in this function); did you mean ‘dummy_steal_clock’?
47 | return static_call(pv_steal_clock)(cpu);
| ^~
| dummy_steal_clock
cc1: some
RE: [PATCH v4 07/15] x86/paravirt: switch time pvops functions to use static_call()
From: Juergen Gross 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
> ---
> 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
> #include
> #include
> +#include
> #include
> #include
> #include
> @@ -445,7 +446,7 @@ static bool __init hv_init_tsc_clocksource(void)
> clocksource_register_hz(_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(_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
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