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

Tom Lendacky
2017-05-30T20:07:33Z

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@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. :)
>

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

Thanks,
Tom