x86/realmode: Decrypt trampoline area if memory encryption is active

When Secure Memory Encryption is enabled, the trampoline area must not
be encrypted. A CPU running in real mode will not be able to decrypt
memory that has been encrypted because it will not be able to use addresses
with the memory encryption mask.

Signed-off-by: Tom Lendacky <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Reviewed-by: Borislav Petkov <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brijesh Singh <[email protected]>
Cc: Dave Young <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Konrad Rzeszutek Wilk <[email protected]>
Cc: Larry Woodman <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Matt Fleming <[email protected]>
Cc: Michael S. Tsirkin <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Radim Krčmář <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Toshimitsu Kani <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: http://lkml.kernel.org/r/c70ffd2614fa77e80df31c9169ca98a9b16ff97c.1500319216.git.thomas.lendacky@amd.com
Signed-off-by: Ingo Molnar <[email protected]>

1 files changed, 8 insertions, 0 deletions

diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c
index cd4be19c36dc..d6ddc7e60884 100644
--- a/arch/x86/realmode/init.c
+++ b/arch/x86/realmode/init.c
@@ -1,6 +1,7 @@
 #include <linux/io.h>
 #include <linux/slab.h>
 #include <linux/memblock.h>
+#include <linux/mem_encrypt.h>
 
 #include <asm/set_memory.h>
 #include <asm/pgtable.h>
@@ -59,6 +60,13 @@ static void __init setup_real_mode(void)
 
 	base = (unsigned char *)real_mode_header;
 
+	/*
+	 * If SME is active, the trampoline area will need to be in
+	 * decrypted memory in order to bring up other processors
+	 * successfully.
+	 */
+	set_memory_decrypted((unsigned long)base, size >> PAGE_SHIFT);
+
 	memcpy(base, real_mode_blob, size);
 
 	phys_base = __pa(base);