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Subject[tip:x86/microcode] x86/microcode: Run the AP-loading routine only on the application processors
Commit-ID:  777284b66f2326c7cb4c541e2224b638b562a9d3
Gitweb: http://git.kernel.org/tip/777284b66f2326c7cb4c541e2224b638b562a9d3
Author: Borislav Petkov <bp@suse.de>
AuthorDate: Tue, 25 Oct 2016 11:55:11 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 25 Oct 2016 12:28:57 +0200

x86/microcode: Run the AP-loading routine only on the application processors

cpu_init() is run also on the BSP (in addition to the APs):

x86_64_start_kernel
|-> x86_64_start_reservations
|-> start_kernel
|-> trap_init
|-> cpu_init
|-> load_ucode_ap
...

but we run the AP (Application Processors) microcode loading routine
there too even though we have a BSP-specific routine for that:
load_ucode_bsp().

Which is unnecessary. So let's limit the AP microcode loading routine to
the APs only.

Remove a useless comment while at it.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@kernel.org>
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: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20161025095522.11964-2-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/cpu/common.c | 7 ++-----
arch/x86/kernel/cpu/microcode/amd.c | 5 -----
2 files changed, 2 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 9bd910a..1a1d668 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1462,11 +1462,8 @@ void cpu_init(void)
*/
cr4_init_shadow();

- /*
- * Load microcode on this cpu if a valid microcode is available.
- * This is early microcode loading procedure.
- */
- load_ucode_ap();
+ if (cpu)
+ load_ucode_ap();

t = &per_cpu(cpu_tss, cpu);
oist = &per_cpu(orig_ist, cpu);
diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c
index 620ab06..6b3929e 100644
--- a/arch/x86/kernel/cpu/microcode/amd.c
+++ b/arch/x86/kernel/cpu/microcode/amd.c
@@ -357,17 +357,12 @@ static void __init get_bsp_sig(void)
#else
void load_ucode_amd_ap(void)
{
- unsigned int cpu = smp_processor_id();
struct equiv_cpu_entry *eq;
struct microcode_amd *mc;
u8 *cont = container;
u32 rev, eax;
u16 eq_id;

- /* Exit if called on the BSP. */
- if (!cpu)
- return;
-
if (!container)
return;

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