[tip:x86/asm] x86/realmode: Don't decrypt trampoline area under SEV

[tip-bot for Tom Lendacky]

Commit-ID:  fcdcd6cdd98ff4d0cf876f863024a2fb0b491d41
Gitweb:     https://git.kernel.org/tip/fcdcd6cdd98ff4d0cf876f863024a2fb0b491d41
Author:     Tom Lendacky <thomas.lendacky@xxxxxxx>
AuthorDate: Fri, 20 Oct 2017 09:30:46 -0500
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Tue, 7 Nov 2017 15:35:55 +0100

x86/realmode: Don't decrypt trampoline area under SEV

When SEV is active the trampoline area will need to be in encrypted
memory so only mark the area decrypted if SME is active.

Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Borislav Petkov <bp@xxxxxxx>
Tested-by: Borislav Petkov <bp@xxxxxxx>
Cc: Laura Abbott <labbott@xxxxxxxxxx>
Cc: kvm@xxxxxxxxxxxxxxx
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20171020143059.3291-5-brijesh.singh@xxxxxxx

---
 arch/x86/realmode/init.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c
index ed84d39..d101058 100644
--- a/arch/x86/realmode/init.c
+++ b/arch/x86/realmode/init.c
@@ -64,9 +64,10 @@ static void __init setup_real_mode(void)
 	/*
 	 * If SME is active, the trampoline area will need to be in
 	 * decrypted memory in order to bring up other processors
-	 * successfully.
+	 * successfully. This is not needed for SEV.
 	 */
-	set_memory_decrypted((unsigned long)base, size >> PAGE_SHIFT);
+	if (sme_active())
+		set_memory_decrypted((unsigned long)base, size >> PAGE_SHIFT);
 
 	memcpy(base, real_mode_blob, size);