Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757480AbeAIBt0 (ORCPT + 1 other); Mon, 8 Jan 2018 20:49:26 -0500 Received: from mga06.intel.com ([134.134.136.31]:22660 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755879AbeAIBtZ (ORCPT ); Mon, 8 Jan 2018 20:49:25 -0500 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.46,333,1511856000"; d="scan'208";a="193417061" Date: Mon, 8 Jan 2018 17:49:16 -0800 From: Andi Kleen To: "Woodhouse, David" Cc: "torvalds@linux-foundation.org" , "linux-kernel@vger.kernel.org" , "peterz@infradead.org" , "tim.c.chen@linux.intel.com" , "tglx@linutronix.de" , "riel@redhat.com" , "keescook@google.com" , "gnomes@lxorguk.ukuu.org.uk" , "pjt@google.com" , "dave.hansen@intel.com" , "luto@amacapital.net" , "jikos@kernel.org" , "gregkh@linux-foundation.org" Subject: Re: [PATCH v6 11/10] x86/retpoline: Avoid return buffer underflows on context switch II Message-ID: <20180109014916.GI6718@tassilo.jf.intel.com> References: <1515363085-4219-1-git-send-email-dwmw@amazon.co.uk> <1515455051.15588.7.camel@infradead.org> <1515455902.4423.59.camel@amazon.co.uk> <20180109004415.GG6718@tassilo.jf.intel.com> <20180109011602.GH6718@tassilo.jf.intel.com> <20180109012122.GA18313@tassilo.jf.intel.com> <1515460999.4423.104.camel@amazon.co.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1515460999.4423.104.camel@amazon.co.uk> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: > > On Skylake and Broadwell when the RSB underflows it will fall back to the? > > indirect branch predictor, which can be poisoned and we try to avoid > > using with retpoline. So we try to avoid underflows, and this filling > > helps us with that. > > That's no longer true for Broadwell with the latest microcode, right? That's right. -Andi