linux-kernel - Re: [PATCH 1/7] x86/vm86: Clean up saved

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Message-ID: <CAMzpN2gTZGpCDghC5488ejCrj_S2La4mKf1X+SrO0p1Mh4t0HQ@mail.gmail.com>
Date:	Thu, 16 Jul 2015 11:57:36 -0400
From:	Brian Gerst <brgerst@...il.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 1/7] x86/vm86: Clean up saved_fs/gs

On Thu, Jul 16, 2015 at 11:45 AM, Andy Lutomirski <luto@...capital.net> wrote:
> On Thu, Jul 16, 2015 at 4:46 AM, Brian Gerst <brgerst@...il.com> wrote:
>> There is no need to save FS and non-lazy GS outside the 32-bit regs.  Lazy GS
>> still needs to be saved because it wasn't saved on syscall entry.
>
> I think I'm missing something.  Why can't you just lazy_save_gs into regs32->gs?
>
> --Andy

That is probably a better idea.  The gs field exists in pt_regs but is
unused in lazy mode.  Could also change switch_to() to store GS in
pt_regs instead of thread.gs, which would simplify ptrace a bit.

--
Brian Gerst
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