Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752204AbeAEQf0 (ORCPT + 1 other); Fri, 5 Jan 2018 11:35:26 -0500 Received: from mail-io0-f193.google.com ([209.85.223.193]:40070 "EHLO mail-io0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751933AbeAEQfZ (ORCPT ); Fri, 5 Jan 2018 11:35:25 -0500 X-Google-Smtp-Source: ACJfBovnho9u/HtkpC3eD487lQsxcTn+07RScithdlkadOtGuc9wSU9s0SdVF+34EqhZ2IX5Fu2ku73KR9wC1GnArao= MIME-Version: 1.0 In-Reply-To: <20180105160746.23786.11850.stgit@tlendack-t1.amdoffice.net> References: <20180105160736.23786.45026.stgit@tlendack-t1.amdoffice.net> <20180105160746.23786.11850.stgit@tlendack-t1.amdoffice.net> From: Brian Gerst Date: Fri, 5 Jan 2018 11:35:24 -0500 Message-ID: Subject: Re: [PATCH v1 1/3] x86/cpu/AMD: Make LFENCE a serializing instruction To: Tom Lendacky Cc: "the arch/x86 maintainers" , Linux Kernel Mailing List , Peter Zijlstra , Linus Torvalds , Dave Hansen , Borislav Petkov , Thomas Gleixner , Tim Chen , Greg Kroah-Hartman , David Woodhouse , Paul Turner Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On Fri, Jan 5, 2018 at 11:07 AM, Tom Lendacky wrote: > To aid in speculation control, make LFENCE a serializing instruction. > This is done by setting bit 1 of MSR 0xc0011029 (DE_CFG). Some families > that support LFENCE do not have this MSR. For these families, the LFENCE > instruction is already serializing. Does this require a microcode update? -- Brian Gerst