linux-kernel - Re: [RFC PATCH 4/4] treewide: Use clocksource id for struct system_counterval

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Message-ID: <87cyyj1s40.ffs@tglx>
Date:   Fri, 15 Sep 2023 15:30:23 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Hilber <peter.hilber@...nsynergy.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        kvmarm@...ts.linux.dev
Cc:     Peter Hilber <peter.hilber@...nsynergy.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Richard Cochran <richardcochran@...il.com>,
        John Stultz <jstultz@...gle.com>,
        Stephen Boyd <sboyd@...nel.org>, netdev@...r.kernel.org,
        Marc Zyngier <maz@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [RFC PATCH 4/4] treewide: Use clocksource id for struct
 system_counterval_t

Peter!

On Fri, Aug 18 2023 at 03:12, Peter Hilber wrote:
> --- a/arch/x86/kernel/tsc.c
> +++ b/arch/x86/kernel/tsc.c
> @@ -1313,7 +1313,7 @@ struct system_counterval_t convert_art_to_tsc(u64 art)
>  	res += tmp + art_to_tsc_offset;
>  
>  	return (struct system_counterval_t) {
> -		.cs = have_art ? &clocksource_tsc : NULL,
> +		.cs_id = have_art ? CSID_TSC : CSID_GENERIC,
>  		.cycles = res

Can you please change all of this so that:

    patch 1:   Adds cs_id to struct system_counterval_t
    patch 2-4: Add the clocksource ID and set the cs_id field
    patch 5:   Switches the core to evaluate cs_id
    patch 6:   Remove the cs field from system_counterval_t


> --- a/include/linux/timekeeping.h
> +++ b/include/linux/timekeeping.h
> @@ -270,12 +270,12 @@ struct system_device_crosststamp {
>   * struct system_counterval_t - system counter value with the pointer to the
>   *				corresponding clocksource
>   * @cycles:	System counter value
> - * @cs:		Clocksource corresponding to system counter value. Used by
> + * @cs_id:	Clocksource corresponding to system counter value. Used by
>   *		timekeeping code to verify comparibility of two cycle values

That comment is inaccurate. It's not longer the clocksource itself. It's
the ID which is used for validation.

Thanks,

        tglx