From: Borislav Petkov <bp@alien8.de>
To: Rik van Riel <riel@surriel.com>
Cc: Dave Hansen <dave.hansen@intel.com>,
x86@kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com,
Thomas Gleixner <tglx@linutronix.de>, Dave Jones <dsj@fb.com>,
Andy Lutomirski <luto@kernel.org>
Subject: Re: [PATCH v2] x86,mm: print likely CPU at segfault time
Date: Fri, 5 Aug 2022 15:25:52 +0200 [thread overview]
Message-ID: <Yu0aYIbCAjFtEBVZ@zn.tnic> (raw)
In-Reply-To: <2239a6e4f5e9d12ef7a55da6dba716df681201ff.camel@surriel.com>
On Fri, Aug 05, 2022 at 08:53:46AM -0400, Rik van Riel wrote:
> Having a small percentage of the segfaults show up on
> cores other than the broken one does not cause issues with
> detection or diagnosis.
I'm sorry but I'm not buying any of this: this should either be 100%
correct or it can stay on your kernels.
> We could, but then we would be reading the CPU number
> on every page fault, just in case it's a segfault.
>
> That does not seem like a worthwhile tradeoff, given
> how much of a hot path page faults are, and how rare
> segfaults are.
Oh wow, a whopping single instruction:
movl %gs:cpu_number(%rip), %eax # cpu_number, pfo_val__
What tradeoff?
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
prev parent reply other threads:[~2022-08-05 13:26 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-04 19:54 [PATCH v2] x86,mm: print likely CPU at segfault time Rik van Riel
2022-08-04 20:17 ` Ingo Molnar
2022-08-05 3:01 ` Rik van Riel
2022-08-05 7:59 ` Ingo Molnar
2022-08-05 12:54 ` Rik van Riel
2022-08-05 10:08 ` Borislav Petkov
2022-08-05 12:53 ` Rik van Riel
2022-08-05 13:25 ` Borislav Petkov [this message]
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