linux-kernel - Re: [RFC PATCH] x86/tsc: use topology_max

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <ff269ad9-2811-e427-3bb9-5b4c978e80bf@intel.com>
Date:   Mon, 17 Oct 2022 16:15:24 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Feng Tang <feng.tang@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     rui.zhang@...el.com, tim.c.chen@...el.com, liaoyu15@...wei.com
Subject: Re: [RFC PATCH] x86/tsc: use topology_max_packages() in tsc watchdog
 check

On 10/17/22 06:29, Feng Tang wrote:
> +	if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) &&
> +	    boot_cpu_has(X86_FEATURE_NONSTOP_TSC) &&
> +	    boot_cpu_has(X86_FEATURE_TSC_ADJUST) &&
> +	    topology_max_packages() <= 2)
> +		clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;

I couldn't help but notice the comment in here:

> void __init calculate_max_logical_packages(void)
> {
>         int ncpus;
> 
>         /*
>          * Today neither Intel nor AMD support heterogeneous systems so
>          * extrapolate the boot cpu's data to all packages.
>          */
>         ncpus = cpu_data(0).booted_cores * topology_max_smt_threads();
>         __max_logical_packages = DIV_ROUND_UP(total_cpus, ncpus);
>         pr_info("Max logical packages: %u\n", __max_logical_packages);
> }

Could you double check for me that the Alder Lake combination Core/Atom
CPUs don't count as "heterogeneous systems" in this case?