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

[Tom Lendacky]

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