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SubjectRe: [PATCH v5 00/12] x86/microcode: Early load microcode
On Thu, Dec 20, 2012 at 11:44:20PM -0800, Fenghua Yu wrote:
> From: Fenghua Yu <fenghua.yu@intel.com>
>
> The problem in current microcode loading method is that we load a microcode way,
> way too late; ideally we should load it before turning paging on. This may only
> be practical on 32 bits since we can't get to 64-bit mode without paging on,
> but we should still do it as early as at all possible.
>
> Similarly, we should load the microcode update as early as possible during AP
> bringup and when processors are brought back online after hotplug or S3/S4.
>
> In order to do that, the microcode patch needs to be permanently present in
> kernel memory. Each individual patch is fairly small, so that is OK, but the
> entire blob with support for each CPU is too big. Since only CPU's with same
> model can be in the same platform, we store microcode with the same model as
> BSP. Later on APs can upload microcode from the saved microcodep patches.
>
> Note, however, that Linux users have gotten used to being able to install a
> microcode patch in the field without having a reboot; we support that model too.
>
> In x86_64, this patchset needs early #PF handler set page table patchset. So
> this patchset is based on:
> git://git.kernel.org/pub/scm/linux/kernel/git/yinghai/linux-yinghai.git for-x86-boot
>

A couple of questions - why the usage of native_[read|write]_msr? I get the
__native_cpuid variant, but I am not sure I understand why you are using
the native_* variants. Especially as this code ends up being called on
Xen and lguest (at least on 64-bit) and probably should go through the
paravirt interfaces.

Also the same question for the __native_flush_tlb_global_irq_disabled
- you take parts of it out (the ones dealing with CR4) and end up
calling those directly? Should they perhaps go through the paravirt
interface?

> v5: Call 64 bit load_ucode_bsp() after copy_bootdata() and remove its
> parameter.
>
> v4: Change CPUID_IS macro. Call load_ucode_bsp after load_idt in x86_64. Flush
> tlb after applying microcode.
>
> v3: Change .hex to .bin in 01/10 and 05/10 patches. Fix some compilation
> warnings. In x86_32 mode, access global varialbes by __pa_symobl() and fix
> static string issue in x86_vendor(). Call load_ucode_ap() in real mode as well.
> Add debug info.
>
> v2: Detect vendor before loading microcode. Move some functions from
> microcode_intel_early.c to microcode_intel_lib.c. Change some early loading
> microcode dependencies in Kconfig. Reword doc.
>
> Fenghua Yu (12):
> Documentation/x86: Early load microcode
> x86/microcode_intel.h: Define functions and macros for early loading
> ucode
> x86/common.c: Make have_cpuid_p() a global function
> x86/common.c: load ucode in 64 bit or show loading ucode info in 32
> bit on AP
> x86/microcode_core_early.c: Define interfaces for early loading ucode
> x86/microcode_intel_lib.c: Early update ucode on Intel's CPU
> x86/tlbflush.h: Define __native_flush_tlb_global_irq_disabled()
> x86/microcode_intel_early.c: Early update ucode on Intel's CPU
> x86/head_32.S: Early update ucode in 32-bit
> x86/head64.c: Early update ucode in 64-bit
> x86/mm/init.c: Copy ucode from initrd image to kernel memory
> x86/Kconfig: Configurations to enable/disable the feature
>
> Documentation/x86/early-microcode.txt | 43 ++
> arch/x86/Kconfig | 18 +
> arch/x86/include/asm/microcode.h | 14 +
> arch/x86/include/asm/microcode_intel.h | 85 ++++
> arch/x86/include/asm/processor.h | 8 +
> arch/x86/include/asm/tlbflush.h | 18 +-
> arch/x86/kernel/Makefile | 3 +
> arch/x86/kernel/cpu/common.c | 17 +-
> arch/x86/kernel/head64.c | 6 +
> arch/x86/kernel/head_32.S | 11 +
> arch/x86/kernel/microcode_core.c | 7 +-
> arch/x86/kernel/microcode_core_early.c | 76 +++
> arch/x86/kernel/microcode_intel.c | 198 ++------
> arch/x86/kernel/microcode_intel_early.c | 796 ++++++++++++++++++++++++++++++++
> arch/x86/kernel/microcode_intel_lib.c | 174 +++++++
> arch/x86/mm/init.c | 10 +
> 16 files changed, 1301 insertions(+), 183 deletions(-)
> create mode 100644 Documentation/x86/early-microcode.txt
> create mode 100644 arch/x86/include/asm/microcode_intel.h
> create mode 100644 arch/x86/kernel/microcode_core_early.c
> create mode 100644 arch/x86/kernel/microcode_intel_early.c
> create mode 100644 arch/x86/kernel/microcode_intel_lib.c
>
> --
> 1.8.0.1
>
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