[tip:x86/urgent] x86/microcode/AMD: Reload proper initrd start address

[tip-bot for Borislav Petkov]

Commit-ID:  8877ebdd3f9a3ffc84c4b67562d257c5f553bc49
Gitweb:     http://git.kernel.org/tip/8877ebdd3f9a3ffc84c4b67562d257c5f553bc49
Author:     Borislav Petkov <bp@xxxxxxx>
AuthorDate: Tue, 20 Dec 2016 11:54:30 +0100
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Wed, 21 Dec 2016 10:50:04 +0100

x86/microcode/AMD: Reload proper initrd start address

When we switch to virtual addresses and, especially after
reserve_initrd()->relocate_initrd() have run, we have the updated initrd
address in initrd_start. Use initrd_start then instead of the address
which has been passed to us through boot params. (That still gets used
when we're running the very early routines on the BSP).

Reported-and-tested-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Link: http://lkml.kernel.org/r/20161220144012.lc4cwrg6dphqbyqu@xxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
 arch/x86/kernel/cpu/microcode/core.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index c4bb2f7..2af69d2 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -243,14 +243,12 @@ struct cpio_data find_microcode_in_initrd(const char *path, bool use_pa)
 # endif
 
 	/*
-	 * Did we relocate the ramdisk?
-	 *
-	 * So we possibly relocate the ramdisk *after* applying microcode on the
-	 * BSP so we rely on use_pa (use physical addresses) - even if it is not
-	 * absolutely correct - to determine whether we've done the ramdisk
-	 * relocation already.
+	 * Fixup the start address: after reserve_initrd() runs, initrd_start
+	 * has the virtual address of the beginning of the initrd. It also
+	 * possibly relocates the ramdisk. In either case, initrd_start contains
+	 * the updated address so use that instead.
 	 */
-	if (!use_pa && relocated_ramdisk)
+	if (!use_pa && initrd_start)
 		start = initrd_start;
 
 	return find_cpio_data(path, (void *)start, size, NULL);