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

Borislav Petkov
2017-05-16T17:35:59Z

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@amd.com>
> ---
> 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. :)

--
Regards/Gruss,
Boris.

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