Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935464AbeAHREG (ORCPT + 1 other); Mon, 8 Jan 2018 12:04:06 -0500 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:38932 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934431AbeAHREC (ORCPT ); Mon, 8 Jan 2018 12:04:02 -0500 Date: Mon, 8 Jan 2018 18:03:56 +0100 From: Willy Tarreau To: Thomas Gleixner Cc: linux-kernel@vger.kernel.org, x86@kernel.org, gnomes@lxorguk.ukuu.org.uk, torvalds@linux-foundation.org Subject: Re: [PATCH RFC 1/4] x86/thread_info: add TIF_NOPTI to disable PTI per task Message-ID: <20180108170356.GD10913@1wt.eu> References: <1515427939-10999-1-git-send-email-w@1wt.eu> <1515427939-10999-2-git-send-email-w@1wt.eu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.6.1 (2016-04-27) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On Mon, Jan 08, 2018 at 05:57:11PM +0100, Thomas Gleixner wrote: > On Mon, 8 Jan 2018, Willy Tarreau wrote: > > > This flag indicates that the task will not use isolated page tables. > > > > Signed-off-by: Willy Tarreau > > --- > > arch/x86/include/asm/thread_info.h | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h > > index 0022333..2f92cf1 100644 > > --- a/arch/x86/include/asm/thread_info.h > > +++ b/arch/x86/include/asm/thread_info.h > > @@ -126,6 +126,14 @@ struct thread_info { > > #define _TIF_X32 (1 << TIF_X32) > > #define _TIF_FSCHECK (1 << TIF_FSCHECK) > > > > +/* The following flags only exist on x86-64. We can't use the shift anymore > > Please do not use this horrible comment syle You mean, the fact that there is no '/*' alone on the first line or anything else ? > And what's wrong with (1UL << 32)? It fails when inherited in assembly parts. Initially the test was based on "testq $(_TIF_NOPTI), reg" and 1UL doesn't parse there, which is why I had to abandon it. In the latest patch I dropped "testq" for "bt" so I didn't need the mask anymore and it wouldn't be a problem... until someone wants to use it again. > > + * due to C using signed ints by default and asm using unsigned longs. > > + */ > > +#ifdef CONFIG_X86_64 > > +# define TIF_NOPTI 32 /* disable PTI for this task */ > > No tail comments please. OK but I did exactly like is done for all other flags above :-/ Thanks, Willy