From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752675AbcFNTTV (ORCPT ); Tue, 14 Jun 2016 15:19:21 -0400 Received: from mail.skyhub.de ([78.46.96.112]:56177 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751590AbcFNTTT (ORCPT ); Tue, 14 Jun 2016 15:19:19 -0400 Date: Tue, 14 Jun 2016 21:19:16 +0200 From: Borislav Petkov To: Dave Hansen Cc: One Thousand Gnomes , Lukasz Anaczkowski , linux-kernel@vger.kernel.org, linux-mm@kvack.org, tglx@linutronix.de, mingo@redhat.com, ak@linux.intel.com, kirill.shutemov@linux.intel.com, mhocko@suse.com, akpm@linux-foundation.org, hpa@zytor.com, harish.srinivasappa@intel.com, lukasz.odzioba@intel.com, grzegorz.andrejczuk@intel.com, lukasz.daniluk@intel.com Subject: Re: [PATCH v2] Linux VM workaround for Knights Landing A/D leak Message-ID: <20160614191916.GI30015@pd.tnic> References: <7FB15233-B347-4A87-9506-A9E10D331292@gmail.com> <1465923672-14232-1-git-send-email-lukasz.anaczkowski@intel.com> <57603DC0.9070607@linux.intel.com> <20160614193407.1470d998@lxorguk.ukuu.org.uk> <576052E0.3050408@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <576052E0.3050408@linux.intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 14, 2016 at 11:54:24AM -0700, Dave Hansen wrote: > Lukasz, Borislav suggested using static_cpu_has_bug(), which will do the > alternatives patching. It's definitely the right thing to use here. Yeah, either that or do an alternative_call(null_func, fix_pte_peak, X86_BUG_PTE_LEAK, ...) or so and you'll need a dummy function to call on !X86_BUG_PTE_LEAK CPUs. The static_cpu_has_bug() thing should be most likely a penalty of a single JMP (I have to look at the asm) but then since the callers are inlined, you'll have to patch all those places where *ptep_get_and_clear() get inlined. Shouldn't be a big deal still but... "debug-alternative" and a kvm guest should help you there to get a quick idea. HTH. -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply.