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From:   Thomas Gleixner <tglx@linutronix.de>
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To:     kan.liang@linux.intel.com, jstultz@google.com,
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Cc:     sboyd@kernel.org, eranian@google.com, namhyung@kernel.org,
        ak@linux.intel.com, adrian.hunter@intel.com,
        Kan Liang <kan.liang@linux.intel.com>,
        Ravi Bangoria <ravi.bangoria@amd.com>
Subject: Re: [RFC PATCH V2 4/9] perf/x86: Enable post-processing monotonic
 raw conversion
In-Reply-To: <20230213190754.1836051-5-kan.liang@linux.intel.com>
References: <20230213190754.1836051-1-kan.liang@linux.intel.com>
 <20230213190754.1836051-5-kan.liang@linux.intel.com>
Date:   Tue, 14 Feb 2023 21:02:23 +0100
Message-ID: <875yc4rp68.ffs@tglx>
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X-Mailing-List: linux-kernel@vger.kernel.org

Kan!

On Mon, Feb 13 2023 at 11:07, kan liang wrote:
> From: Kan Liang <kan.liang@linux.intel.com>
> +	} else if (perf_event_hw_time(event)) {
> +		struct ktime_conv mono;
> +
> +		userpg->cap_user_time_mono_raw = 1;
> +		ktime_get_fast_mono_raw_conv(&mono);

What guarantees that the clocksource used by the timekeeping core is
actually TSC? Nothing at all. You cannot make assumptions here.

Thanks,

        tglx