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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Rik van Riel <riel@surriel.com>,
        Dave Hansen <dave.hansen@intel.com>,
        linux-kernel@vger.kernel.org
Cc:     Dave Hansen <dave.hansen@linux.intel.com>,
        Andy Lutomirski <luto@kernel.org>, kernel-team@fb.com,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org
Subject: Re: [PATCH] x86,mm: print likely CPU at segfault time
In-Reply-To: <a9f568139f0bd82cc8460c2c4f831f03a74f2a89.camel@surriel.com>
References: <20210719150041.3c719c94@imladris.surriel.com> <c8e023cb-6f50-36f5-65d4-c5e25b264029@intel.com> <a9f568139f0bd82cc8460c2c4f831f03a74f2a89.camel@surriel.com>
Date:   Wed, 21 Jul 2021 22:38:32 +0200
Message-ID: <87pmvbpflj.ffs@nanos.tec.linutronix.de>
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On Mon, Jul 19 2021 at 15:34, Rik van Riel wrote:

> On Mon, 2021-07-19 at 12:20 -0700, Dave Hansen wrote:
>
>> If it's as trivial as:
>>=20
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0printk(KERN_CONT " on cp=
u/core %d/%d",
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0raw_smp_processor_id(),
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0topology_core_id(raw_smp_processor_id()));
>>=20
>> it would be handy.=C2=A0 But, it's also not hard to look at 10 segfaults,
>> see
>> that they happened only on 2 CPUs and realize that hyperthreading is
>> enabled.
>
> One problem with topology_core_id() is that that, on a
> multi-socket system, the core number may not be unique.

Just add topology_physical_package_id() and you have a complete picture.

Thanks,

        tglx