linux-kernel - Re: [RFC PATCH 0/4] treewide: Use clocksource id for get_device_system

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Message-ID: <CANDhNCo_Z2_tnuCyvu-j=eqOkvDQ+_n2O-=JKpf2Ndqx1m5GqQ@mail.gmail.com>
Date:   Thu, 24 Aug 2023 21:18:32 -0700
From:   John Stultz <jstultz@...gle.com>
To:     Peter Hilber <peter.hilber@...nsynergy.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        kvmarm@...ts.linux.dev, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        netdev@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Richard Cochran <richardcochran@...il.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>, x86@...nel.org,
        Marc Zyngier <maz@...nel.org>,
        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 0/4] treewide: Use clocksource id for get_device_system_crosststamp()

On Thu, Aug 17, 2023 at 6:13 PM Peter Hilber
<peter.hilber@...nsynergy.com> wrote:
>
> This patch series changes struct system_counterval_t to identify the
> clocksource through enum clocksource_ids, rather than through struct
> clocksource *. The net effect of the patch series is that
> get_device_system_crosststamp() callers can supply clocksource ids instead
> of clocksource pointers, which can be problematic to get hold of.

Hey Peter,
  Thanks for sending this out. I'm a little curious though, can you
expand a bit on how clocksource pointers can be problematic to get a
hold of? What exactly is the problem that is motivating this change?

I just worry that switching to an enumeration solution might be
eventually exposing more than we would like to userland.

thanks
-john