x86/boot/compressed/64: Setup a GHCB-based VC Exception handler

Install an exception handler for #VC exception that uses a GHCB. Also
add the infrastructure for handling different exit-codes by decoding
the instruction that caused the exception and error handling.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-24-joro@8bytes.org
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 7101ac6..8289dd4 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1521,6 +1521,7 @@
 	select DYNAMIC_PHYSICAL_MASK
 	select ARCH_USE_MEMREMAP_PROT
 	select ARCH_HAS_FORCE_DMA_UNENCRYPTED
+	select INSTRUCTION_DECODER
 	help
 	  Say yes to enable support for the encryption of system memory.
 	  This requires an AMD processor that supports Secure Memory