linux-kernel - Re: [PATCH 08/10] clocksource/drivers/hyper-v: Handle sched

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Date:   Mon, 1 Feb 2021 18:55:13 +0000
From:   Wei Liu <wei.liu@...nel.org>
To:     Michael Kelley <mikelley@...rosoft.com>
Cc:     sthemmin@...rosoft.com, kys@...rosoft.com, wei.liu@...nel.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        daniel.lezcano@...aro.org, arnd@...db.de,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH 08/10] clocksource/drivers/hyper-v: Handle sched_clock
 differences inline

On Wed, Jan 27, 2021 at 12:23:43PM -0800, Michael Kelley wrote:
[...]
> +/*
> + * 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)

sched_clock_register is not trivial. Having __always_inline here is
going to make the compiled object bloated.

Given this is a static function, I don't think we need to specify any
inline keyword. The compiler should be able to determine whether this
function should be inlined all by itself.

Wei.

> +{
> +#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
> +}
> +
>  static bool __init hv_init_tsc_clocksource(void)
>  {
>  	u64		tsc_msr;
> -- 
> 1.8.3.1
>