[tip:x86/microcode] x86/microcode/intel: Make early loader look for builtin microcode too

[tip-bot for Borislav Petkov]

Commit-ID:  264285ac01673e70557c43ecee338ce97c4c0672
Gitweb:     http://git.kernel.org/tip/264285ac01673e70557c43ecee338ce97c4c0672
Author:     Borislav Petkov <bp@xxxxxxx>
AuthorDate: Wed, 3 Feb 2016 12:33:30 +0100
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 9 Feb 2016 11:41:15 +0100

x86/microcode/intel: Make early loader look for builtin microcode too

Set the initrd @start depending on the presence of an initrd. Otherwise,
builtin microcode loading doesn't work as the start is wrong and we're
using it to compute offset to the microcode blobs.

Tested-by: Thomas Voegtle <tv@xxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 4.4
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1454499225-21544-3-git-send-email-bp@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/kernel/cpu/microcode/intel.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index 044bbbbc..4f4735b 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -551,10 +551,14 @@ scan_microcode(struct mc_saved_data *mc_saved_data, unsigned long *initrd,
 	cd.data = NULL;
 	cd.size = 0;
 
-	cd = find_cpio_data(p, (void *)start, size, &offset);
-	if (!cd.data) {
+	/* try built-in microcode if no initrd */
+	if (!size) {
 		if (!load_builtin_intel_microcode(&cd))
 			return UCODE_ERROR;
+	} else {
+		cd = find_cpio_data(p, (void *)start, size, &offset);
+		if (!cd.data)
+			return UCODE_ERROR;
 	}
 
 	return get_matching_model_microcode(0, start, cd.data, cd.size,
@@ -728,16 +732,20 @@ void __init load_ucode_intel_bsp(void)
 	struct boot_params *p;
 
 	p	= (struct boot_params *)__pa_nodebug(&boot_params);
-	start	= p->hdr.ramdisk_image;
 	size	= p->hdr.ramdisk_size;
 
-	_load_ucode_intel_bsp(
-			(struct mc_saved_data *)__pa_nodebug(&mc_saved_data),
-			(unsigned long *)__pa_nodebug(&mc_saved_in_initrd),
-			start, size);
+	/*
+	 * Set start only if we have an initrd image. We cannot use initrd_start
+	 * because it is not set that early yet.
+	 */
+	start	= (size ? p->hdr.ramdisk_image : 0);
+
+	_load_ucode_intel_bsp((struct mc_saved_data *)__pa_nodebug(&mc_saved_data),
+			      (unsigned long *)__pa_nodebug(&mc_saved_in_initrd),
+			      start, size);
 #else
-	start	= boot_params.hdr.ramdisk_image + PAGE_OFFSET;
 	size	= boot_params.hdr.ramdisk_size;
+	start	= (size ? boot_params.hdr.ramdisk_image + PAGE_OFFSET : 0);
 
 	_load_ucode_intel_bsp(&mc_saved_data, mc_saved_in_initrd, start, size);
 #endif