Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753449AbeAFVqn (ORCPT + 1 other); Sat, 6 Jan 2018 16:46:43 -0500 Received: from userp2120.oracle.com ([156.151.31.85]:38940 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752249AbeAFVql (ORCPT ); Sat, 6 Jan 2018 16:46:41 -0500 Date: Sat, 6 Jan 2018 16:46:18 -0500 From: Konrad Rzeszutek Wilk To: Thomas Gleixner , Linus Torvalds Cc: Dave Hansen , "Van De Ven, Arjan" , Konrad Rzeszutek Wilk , Tim Chen , Andy Lutomirski , Linus Torvalds , Greg KH , Andrea Arcangeli , Andi Kleen , David Woodhouse , "linux-kernel@vger.kernel.org" Subject: Is: Linus, name for 'spectre' variable. Was:Re: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature Message-ID: <20180106214618.GM19213@char.us.oracle.com> References: <20180106144110.GA2592@localhost.localdomain> <742ed1d9-7210-8443-0373-5af74f193ab9@intel.com> <0575AF4FD06DD142AD198903C74E1CC87A56C6FE@ORSMSX103.amr.corp.intel.com> <20180106213227.GJ19213@char.us.oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.8.3 (2017-05-23) X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8766 signatures=668652 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1801060315 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On Sat, Jan 06, 2018 at 10:39:27PM +0100, Thomas Gleixner wrote: > On Sat, 6 Jan 2018, Konrad Rzeszutek Wilk wrote: > > On Sat, Jan 06, 2018 at 08:47:19PM +0100, Thomas Gleixner wrote: > > > On Sat, 6 Jan 2018, Dave Hansen wrote: > > > > > > > On 01/06/2018 09:41 AM, Van De Ven, Arjan wrote: > > > > >>>> .macro DISABLE_IBRS > > > > >>>> - ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_SPEC_CTRL > > > > >>>> + testl $1, dynamic_ibrs > > > > >>> On every system call we end up hammering on this 'dynamic_ibrs' > > > > >>> variable. And it looks like it can be flipped via the IPI mechanism. > > > > >>> > > > > >>> Would it make sense for this to be per-cpu? > > > > >> > > > > >> It's probably better to either just make it __read_mostly or get the > > > > >> static branches that folks were suggesting actually working. > > > > > > > > > > I still wonder if this isn't just better as a boot command line > > > > > > > > It's simpler that way. But, ideally, we want to make it runtime > > > > switchable to match the implementation in the distros. > > > > > > Stop this silly argument please. The distros shipped lots of crap which we > > > dont want to have at all. > > > > > > I told you folks yesterday what I want to see and the sysctl thing is the > > > least on that list and it's not needed for getting the important thing - > > > the protection - to work. > > > > I agree. But this is what customers are told to inspect to see if they > > are impacted. And if in the future versions this goes away or such - they > > will freak out and cause needless escalations. > > That's the result of distros cramming stuff into their kernels without > talking to us. It's their problem to explain that their customers. I am trying to resolve this now for those distros's that haven't crammed these patches in yet and get a resolution on the naming _now_ so they can update it to have the right name from the gecko for the future. Lets rope in the boss. > > We can talks about the sysctl _AFTER_ fixing the real issues. Perhaps we can delegate this to Linus. > > Thanks, > > tglx