linux-kernel - [PATCH 02/17] x86/microcode/intel: Make early loader look for builtin microcode too

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Date:	Wed,  3 Feb 2016 12:33:30 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	X86 ML <x86@...nel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 02/17] x86/microcode/intel: Make early loader look for builtin microcode too

From: Borislav Petkov <bp@...e.de>

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.

Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: <stable@...r.kernel.org> # 4.4
---
 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 044bbbbcbaf1..4f4735bd8698 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
-- 
2.3.5