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Commit 9f3cc2a0 authored by Borislav Petkov's avatar Borislav Petkov Committed by Ingo Molnar
Browse files

Documentation/microcode: Document some aspects for more clarity 



Document that builtin microcode is 64-bit only. Also, improve/add
comments to places.

Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-doc@vger.kernel.org
Link: http://lkml.kernel.org/r/1465225850-7352-10-git-send-email-bp@alien8.de


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent a13004a2

Documentation/x86/early-microcode.txt

+4 −1
Original line number Diff line number Diff line
@@ -45,7 +45,10 @@ Builtin microcode 
=================



We can also load builtin microcode supplied through the regular firmware

builtin method CONFIG_FIRMWARE_IN_KERNEL. Here's an example:

builtin method CONFIG_FIRMWARE_IN_KERNEL. Only 64-bit is currently

supported.



Here's an example:



CONFIG_FIRMWARE_IN_KERNEL=y

CONFIG_EXTRA_FIRMWARE="intel-ucode/06-3a-09 amd-ucode/microcode_amd_fam15h.bin"

arch/x86/kernel/cpu/microcode/intel.c

+9 −7
Original line number Diff line number Diff line
@@ -40,9 +40,13 @@ 
#include <asm/msr.h>



/*

 * Temporary microcode blobs pointers storage. We note here the pointers to

 * microcode blobs we've got from whatever storage (detached initrd, builtin).

 * Later on, we put those into final storage mc_saved_data.mc_saved.

 * Temporary microcode blobs pointers storage. We note here during early load

 * the pointers to microcode blobs we've got from whatever storage (detached

 * initrd, builtin). Later on, we put those into final storage

 * mc_saved_data.mc_saved.

 *

 * Important: those are offsets from the beginning of initrd or absolute

 * addresses within the kernel image when built-in.

 */

static unsigned long mc_tmp_ptrs[MAX_UCODE_COUNT];
@@ -57,6 +61,7 @@ static struct ucode_blobs { 
	bool valid;

} blobs;



/* Go through saved patches and find the one suitable for the current CPU. */

static enum ucode_state

find_microcode_patch(struct microcode_intel **saved,

		     unsigned int num_saved, struct ucode_cpu_info *uci)
@@ -466,6 +471,7 @@ static void show_saved_mc(void) 
static void save_mc_for_early(u8 *mc)

{

#ifdef CONFIG_HOTPLUG_CPU

	/* Synchronization during CPU hotplug. */

	static DEFINE_MUTEX(x86_cpu_microcode_mutex);



	struct microcode_intel *mc_saved_tmp[MAX_UCODE_COUNT];
@@ -474,10 +480,6 @@ static void save_mc_for_early(u8 *mc) 
	struct microcode_intel **mc_saved;

	int ret, i;



	/*

	 * Hold hotplug lock so mc_saved_data is not accessed by a CPU in

	 * hotplug.

	 */

	mutex_lock(&x86_cpu_microcode_mutex);



	mc_saved_count_init = mc_saved_data.num_saved;