linux-kernel - Re: [PATCH 1/5] x86/entry/32: Clean up enable_sep

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Message-ID: <CALCETrX-VMDNJJzoiEO3KqpA+B7+tbz=Lh07gvSX3yWvqGSvyg@mail.gmail.com>
Date:	Thu, 23 Jul 2015 09:02:13 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Willy Tarreau <w@....eu>, Borislav Petkov <bp@...en8.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 1/5] x86/entry/32: Clean up enable_sep_cpu to prepare for
 64-bit merge

On Thu, Jul 23, 2015 at 8:56 AM, Steven Rostedt <rostedt@...dmis.org> wrote:
> On Thu, 23 Jul 2015 08:31:39 -0700
> Andy Lutomirski <luto@...nel.org> wrote:
>
>> Switch from wrmsr to wrmsrl_safe to prepare to merge the 32-bit and
>> 64-bit code, and use __KERNEL_CS explicitly to initialize
>> MSR_IA32_SYSENTER_CS.  While we're at it, tweak the whitespace a
>> bit.
>
> Saying "prepare to merge the 32-bit and 64-bit" isn't that informative
> to why this patch is needed. Can you please describe in the change log
> what can fault with the wrmsr call, when we do the merge?

Oh...

Nothing can fault in the wrmsr as far as I know, but maybe there's a
CPU out there that advertises SEP but doesn't have the MSRs.

Ingo, Thomas, want a v2 that explains that the wrmsr_safe is there for
consistency but that I don't know why 32bit does it?  Another option
would be to remove the _safe from the 32-bit version.

--Andy
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