*** 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 3-6 are meant to improve the situation. Patch 3 cleans
up the Intel microcode loader and the rest (which depend on patch 3)
stops using CPUID in sync_core() altogether.
Changes from v1:
- Fix Xen
- Add timing info to the changelog (hint: 2x speedup)
- Document patch 1 a bit better.
Andy Lutomirski (6):
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 cpuid_eax(1)
x86/paravirt: Make sync_core() be a paravirt op
x86/xen: Add a Xen-specific sync_core() implementation
x86/asm: Change sync_core() to use MOV to CR2 to serialize
arch/x86/boot/cpu.c | 6 ------
arch/x86/include/asm/paravirt.h | 5 +++++
arch/x86/include/asm/paravirt_types.h | 2 ++
arch/x86/include/asm/processor.h | 34 ++++++++++------------------------
arch/x86/kernel/cpu/microcode/intel.c | 6 +++---
arch/x86/kernel/paravirt.c | 2 ++
arch/x86/xen/enlighten.c | 35 +++++++++++++++++++++++++++++++++++
7 files changed, 57 insertions(+), 33 deletions(-)
--
2.9.3
