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From: Thomas Gleixner <tglx@linutronix.de>
To: Ira Weiny <ira.weiny@intel.com>, Borislav Petkov <bp@alien8.de>
Cc: Rik van Riel <riel@surriel.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	x86@kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: Re: [RFC PATCH 2/5] entry: Add calls for save/restore auxiliary pt_regs
Date: Wed, 10 Aug 2022 01:53:49 +0200	[thread overview]
Message-ID: <87czd9q8he.ffs@tglx> (raw)
In-Reply-To: <YvLWX4NiqReB5CHB@iweiny-desk3>

On Tue, Aug 09 2022 at 14:49, Ira Weiny wrote:
> On Tue, Aug 09, 2022 at 08:49:47PM +0200, Borislav Petkov wrote:
>> Why does that need to run with instrumentation enabled?
>
> This does not.
>
> Am I wrong that instrumentation begin/end are 0 overhead in production builds?

instrumentation_begin/end() are annotations and never emit executable
code. Neither in production nor in debug builds. Why keep you harping on
this question? Is it so hard to figure out what it does?

But that's not the question at all. The question is where auxregs need
to be set up.

Once the entry code leaves non-instrumentable code it's obviously
desired to have consistent state for instrumentation.

This obviously applies also to the auxreg space unless there is a
compelling reason why this is not required.

Thanks,

        tglx

  reply	other threads:[~2022-08-09 23:53 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-05 17:30 [RFC PATCH 0/5] Print CPU at segfault time ira.weiny
2022-08-05 17:30 ` [RFC PATCH 1/5] entry: Pass pt_regs to irqentry_exit_cond_resched() ira.weiny
2022-08-05 18:33   ` Rik van Riel
2022-08-08 10:38   ` Borislav Petkov
2022-08-08 17:34     ` Ira Weiny
2022-08-08 17:38       ` Borislav Petkov
2022-08-08 17:43         ` Dave Hansen
2022-08-08 17:52           ` Borislav Petkov
2022-08-09 23:18     ` Thomas Gleixner
2022-08-10  7:25       ` Thomas Gleixner
2022-08-05 17:30 ` [RFC PATCH 2/5] entry: Add calls for save/restore auxiliary pt_regs ira.weiny
2022-08-05 18:34   ` Rik van Riel
2022-08-09 12:05   ` Borislav Petkov
2022-08-09 18:38     ` Ira Weiny
2022-08-09 18:49       ` Borislav Petkov
2022-08-09 21:14         ` Thomas Gleixner
2022-08-09 21:38           ` Borislav Petkov
2022-08-09 22:33             ` Ira Weiny
2022-08-09 21:49         ` Ira Weiny
2022-08-09 23:53           ` Thomas Gleixner [this message]
2022-08-05 17:30 ` [RFC PATCH 3/5] x86/entry: Add auxiliary pt_regs space ira.weiny
2022-08-05 18:45   ` Rik van Riel
2022-08-05 17:30 ` [RFC PATCH 4/5] x86,mm: print likely CPU at segfault time ira.weiny
2022-08-05 17:30 ` [RFC PATCH 5/5] x86/entry: Store CPU info on exception entry ira.weiny
2022-08-05 18:46   ` Rik van Riel
2022-08-05 18:47   ` Dave Hansen
2022-08-06  9:01     ` Ingo Molnar
2022-08-06  9:11       ` Borislav Petkov
2022-08-07 10:02         ` Ingo Molnar
2022-08-07 10:35           ` Borislav Petkov
2022-08-07 20:02             ` Ira Weiny
2022-08-08 11:03               ` Ingo Molnar
2022-08-08 12:01                 ` Borislav Petkov
2022-08-09 20:06                   ` Thomas Gleixner
2022-08-08 16:16                 ` Dave Hansen
2022-08-08 17:24                   ` Rik van Riel
2022-08-09 21:19                   ` Andy Lutomirski

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