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

From: Jürgen Groß
Date: Tue Jan 19 2021 - 06:50:40 EST

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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