x86/microcode/amd: Extract current patch level read to a function

Pave the way for checking the current patch level of the
microcode in a core. We want to be able to do stuff depending on
the patch level - in this case decide whether to update or not.
But that will be added in a later patch.

Drop unused local var uci assignment, while at it.

Integrate a fix for 32-bit and CONFIG_PARAVIRT from Takashi Iwai:

 Use native_rdmsr() in check_current_patch_level() because with
 CONFIG_PARAVIRT enabled and on 32-bit, where we run before
 paging has been enabled, we cannot deref pv_info yet. Or we
 could, but we'd need to access its physical address. This way of
 fixing it is simpler. See:

   https://bugzilla.suse.com/show_bug.cgi?id=943179 for the background.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Takashi Iwai <tiwai@suse.com>:
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Link: http://lkml.kernel.org/r/1444641762-9437-6-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/x86/include/asm/microcode_amd.h b/arch/x86/include/asm/microcode_amd.h
index ac6d328977a6..9b214e10d499 100644
--- a/arch/x86/include/asm/microcode_amd.h
+++ b/arch/x86/include/asm/microcode_amd.h
@@ -76,4 +76,5 @@ static inline int __init save_microcode_in_initrd_amd(void) { return -EINVAL; }
 void reload_ucode_amd(void) {}
 #endif
 
+extern bool check_current_patch_level(u32 *rev);
 #endif /* _ASM_X86_MICROCODE_AMD_H */