[PATCH 0/4] CPUID-less CPU fixes and improvements

From: Andy Lutomirski
Date: Wed Nov 30 2016 - 15:35:10 EST

*** 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.

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 and 4 are meant to improve the situation. Patch 3 cleans
up the Intel microcode loader and patch 4 (which depends on patch 3)
stops using CPUID in sync_core() altogether.

Andy Lutomirski (4):
x86/asm/32: Make sync_core() handle missing CPUID on all 32-bit
Revert "x86/boot: Fail the boot if !M486 and CPUID is missing"
x86/microcode/intel: Replace sync_core() with cpuid_eax(1)
x86/asm: Change sync_core() to use MOV to CR2 to serialize

arch/x86/boot/cpu.c | 6 ------
arch/x86/include/asm/processor.h | 31 ++++++++-----------------------
arch/x86/kernel/cpu/microcode/intel.c | 6 +++---
3 files changed, 11 insertions(+), 32 deletions(-)