From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751445Ab1GXQQn (ORCPT ); Sun, 24 Jul 2011 12:16:43 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:51565 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750769Ab1GXQQh (ORCPT ); Sun, 24 Jul 2011 12:16:37 -0400 Date: Sun, 24 Jul 2011 09:16:26 -0700 From: Andrew Morton To: Borislav Petkov Cc: Ingo Molnar , Linus Torvalds , "H. Peter Anvin" , Thomas Gleixner , LKML , "Przywara, Andre" , "Pohlack, Martin" Subject: Re: [PATCH] x86, AMD: Correct F15h IC aliasing issue Message-Id: <20110724091626.c6829ebe.akpm@linux-foundation.org> In-Reply-To: <20110724134046.GA10583@aftab> References: <1311340547-7861-1-git-send-email-bp@amd64.org> <20110724111350.GD21120@elte.hu> <20110724134046.GA10583@aftab> X-Mailer: Sylpheed 2.7.1 (GTK+ 2.18.9; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 24 Jul 2011 15:40:46 +0200 Borislav Petkov wrote: > > > + unalias_va_addr > > > + [X86-64] Unalias VA address by clearing slice [14:12] > > > + 1: only on 32-bit > > > + 2: only on 64-bit > > > + off: disabled on both 32 and 64-bit How much performance difference does this actually make? > > This says nothing about why it's cleared, what it does and why one > > would want to handle it differently on 32-bit and 64-bit. > > This is there in case users care more about the 3bits ASLR granularity > than invalidations amount, for example. To make this decision the users will want to know how much their computers will slow down. We should tell them.