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

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Date:   Tue, 16 May 2017 19:35:41 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     linux-arch@...r.kernel.org, linux-efi@...r.kernel.org,
        kvm@...r.kernel.org, linux-doc@...r.kernel.org, x86@...nel.org,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        iommu@...ts.linux-foundation.org, Rik van Riel <riel@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Toshimitsu Kani <toshi.kani@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Larry Woodman <lwoodman@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dave Young <dyoung@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH v5 26/32] x86, drm, fbdev: Do not specify encrypted
 memory for video mappings

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@....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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