[RFC PATCH v2 17/20] x86: Do not specify encrypted memory for VGA mapping

[Tom Lendacky <thomas.lendacky@amd.com>]

Since the VGA memory needs to be accessed unencrypted be sure that the
memory encryption mask is not set for the VGA range being mapped.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 arch/x86/include/asm/vga.h |   13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/x86/include/asm/vga.h b/arch/x86/include/asm/vga.h
index c4b9dc2..55fe164 100644
--- a/arch/x86/include/asm/vga.h
+++ b/arch/x86/include/asm/vga.h
@@ -7,12 +7,25 @@
 #ifndef _ASM_X86_VGA_H
 #define _ASM_X86_VGA_H
 
+#include <asm/mem_encrypt.h>
+
 /*
  *	On the PC, we can just recalculate addresses and then
  *	access the videoram directly without any black magic.
+ *	To support memory encryption however, we need to access
+ *	the videoram as un-encrypted memory.
  */
 
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+#define VGA_MAP_MEM(x, s)					\
+({								\
+	unsigned long start = (unsigned long)phys_to_virt(x);	\
+	sme_set_mem_dec((void *)start, s);			\
+	start;							\
+})
+#else
 #define VGA_MAP_MEM(x, s) (unsigned long)phys_to_virt(x)
+#endif
 
 #define vga_readb(x) (*(x))
 #define vga_writeb(x, y) (*(y) = (x))