On 02/03/2021 02:38, Michael Kelley wrote:
From: Daniel Lezcano <redacted> Sent: Monday, March 1, 2021 6:25 AM
quoted
On 01/03/2021 02:15, Michael Kelley wrote:
quoted
While the Hyper-V Reference TSC code is architecture neutral, the
pv_ops.time.sched_clock() function is implemented for x86/x64, but not
for ARM64. Current code calls a utility function under arch/x86 (and
coming, under arch/arm64) to handle the difference.
Change this approach to handle the difference inline based on whether
GENERIC_SCHED_CLOCK is present. The new approach removes code under
arch/* since the difference is tied more to the specifics of the Linux
implementation than to the architecture.
No functional change.
Signed-off-by: Michael Kelley <redacted>
Reviewed-by: Boqun Feng <redacted>
---
[ ... ]
quoted
+/*
+ * 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_GENERIC_SCHED_CLOCK
+ /*
+ * We're on an architecture with generic sched clock (not x86/x64).
+ * The Hyper-V sched clock read function returns nanoseconds, not
+ * the normal 100ns units of the Hyper-V synthetic clock.
+ */
+ sched_clock_register(sched_clock, 64, NSEC_PER_SEC);
+#else
+#ifdef CONFIG_PARAVIRT
+ /* We're on x86/x64 *and* using PV ops */
+ pv_ops.time.sched_clock = sched_clock;
+#endif
+#endif
+}
Please refer to:
Documentation/process/coding-style.rst
Section 21)
[ ... ]
Prefer to compile out entire functions, rather than portions of
functions or portions of expressions.
[ ... ]
OK. I'll rework the #ifdef in v3 of the patch set. Is the following
the preferred approach?
Yes but with an indentation and comment to describe the section end.
eg.
#ifdef A
#else
# ifdef B
...
# else
# endif /* B */
#endif /* A */
#ifdef CONFIG_GENERIC_SCHED_CLOCK
static __always_inline void hv_setup_sched_clock(void *sched_clock)
{
sched_clock_register(sched_clock, 64 NSEC_PER_SEC);
}
#else
#ifdef CONFIG_PARAVIRT
static __always_inline void hv_setup_sched_clock(void *sched_clock)
{
pv_ops.time.sched_clock = sched_clock:
}
#else
static __always_inline void hv_setup_sched_clock(void *sched_clock) {}
#endif
#endif
Or
#ifdef CONFIG_GENERIC_SCHED_CLOCK
...
#elif defined CONFIG_PARAVIRT
...
#else /* !CONFIG_GENERIC_SCHED_CLOCK && !CONFIG_PARAVIRT */
...
#endif /* CONFIG_GENERIC_SCHED_CLOCK */
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