Re: [PATCH v5 26/32] x86, drm, fbdev: Do not specify encrypted memory for video mappings

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On 5/16/2017 12:35 PM, Borislav Petkov wrote:
On Tue, Apr 18, 2017 at 04:20:56PM -0500, Tom Lendacky wrote:
Since video memory needs to be accessed decrypted, be sure that the
memory encryption mask is not set for the video ranges.

Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
---
  arch/x86/include/asm/vga.h       |   13 +++++++++++++
  arch/x86/mm/pageattr.c           |    2 ++
  drivers/gpu/drm/drm_gem.c        |    2 ++
  drivers/gpu/drm/drm_vm.c         |    4 ++++
  drivers/gpu/drm/ttm/ttm_bo_vm.c  |    7 +++++--
  drivers/gpu/drm/udl/udl_fb.c     |    4 ++++
  drivers/video/fbdev/core/fbmem.c |   12 ++++++++++++
  7 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/vga.h b/arch/x86/include/asm/vga.h
index c4b9dc2..5c7567a 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/cacheflush.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 decrypted memory.
   */
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+#define VGA_MAP_MEM(x, s)					\
+({								\
+	unsigned long start = (unsigned long)phys_to_virt(x);	\
+	set_memory_decrypted(start, (s) >> PAGE_SHIFT);		\
+	start;							\
+})
+#else
  #define VGA_MAP_MEM(x, s) (unsigned long)phys_to_virt(x)
+#endif

Can we push the check in and save us the ifdeffery?

#define VGA_MAP_MEM(x, s)                                       \
({                                                              \
         unsigned long start = (unsigned long)phys_to_virt(x);   \
                                                                 \
         if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT))                 \
                 set_memory_decrypted(start, (s) >> PAGE_SHIFT); \
                                                                 \
         start;                                                  \
})

It does build here. :)


That works for me and it's a lot cleaner.  I'll make the change.

Thanks,
Tom



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