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

From: Tom Lendacky
Date: Mon Aug 22 2016 - 19:14:25 EST


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@xxxxxxx>
---
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))