Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752226AbcLEVcs (ORCPT ); Mon, 5 Dec 2016 16:32:48 -0500 Received: from mail.kernel.org ([198.145.29.136]:54582 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751328AbcLEVcr (ORCPT ); Mon, 5 Dec 2016 16:32:47 -0500 From: Andy Lutomirski To: x86@kernel.org Cc: One Thousand Gnomes , Borislav Petkov , "linux-kernel@vger.kernel.org" , Brian Gerst , Matthew Whitehead , Henrique de Moraes Holschuh , Peter Zijlstra , xen-devel , Juergen Gross , Boris Ostrovsky , Andrew Cooper , Andy Lutomirski Subject: [PATCH v3 0/4] CPUID-less CPU/sync_core fixes and improvements Date: Mon, 5 Dec 2016 13:32:39 -0800 Message-Id: X-Mailer: git-send-email 2.9.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1464 Lines: 39 *** PATCHES 1 and 2 MAY BE 4.9 MATERIAL *** Alan Cox pointed out that the 486 isn't the only supported CPU that doesn't have CPUID. Let's clean up the mess and make everything faster while we're at it. Patch 1 is intended to be an easy fix: it makes sync_core() work without CPUID on all 32-bit kernels. It should be quite safe. This will have a negligible performance cost during boot on kernels built for newer CPUs. With this in place, patch 2 reverts the buggy 486 check I added. Patches 3-4 are meant to improve the situation. Patch 3 cleans up the Intel microcode loader and the patch 4 (which depends on patch 3 to work correctly) stops using CPUID in sync_core() altogether. Changes from v2: - Switch to IRET-to-self and get rid of all the paravirt code. - Further immprove the sync_core() comment. Changes from v1: - Fix Xen - Add timing info to the changelog (hint: 2x speedup) - Document patch 1 a bit better. Andy Lutomirski (4): x86/asm/32: Make sync_core() handle missing CPUID on all 32-bit kernels Revert "x86/boot: Fail the boot if !M486 and CPUID is missing" x86/microcode/intel: Replace sync_core() with native_cpuid() x86/asm: Rewrite sync_core() to use IRET-to-self arch/x86/boot/cpu.c | 6 --- arch/x86/include/asm/processor.h | 77 +++++++++++++++++++++++++---------- arch/x86/kernel/cpu/microcode/intel.c | 26 ++++++++++-- 3 files changed, 78 insertions(+), 31 deletions(-) -- 2.9.3