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>

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 9bd910a..1a1d668 100644 (file)
--- 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 (file)
--- 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;