linux-kernel - Re: [PATCHv3 1/3] x86/mm/encrypt: Move page table helpers into separate translation unit

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Date:   Tue, 30 Jan 2018 16:26:03 -0600
From:   Tom Lendacky <thomas.lendacky@....com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Borislav Petkov <bp@...e.de>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3 1/3] x86/mm/encrypt: Move page table helpers into
 separate translation unit

On 1/24/2018 10:36 AM, Kirill A. Shutemov wrote:
> There are bunch of functions in mem_encrypt.c that operate on the
> identity mapping, which means they want virtual addresses to be equal to
> physical one, without PAGE_OFFSET shift.
> 
> We also need to avoid paravirtualizaion call there.
> 
> Getting this done is tricky. We cannot use usual page table helpers.
> It forces us to open-code a lot of things. It makes code ugly and hard
> to modify.
> 
> We can get it work with the page table helpers, but it requires few
> preprocessor tricks. These tricks may have side effects for the rest of
> the file.
> 
> Let's isolate such functions into own translation unit.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

Just one minor comment at the end.  With that change:

Reviewed-by: Tom Lendacky <thomas.lendacky@....com>

> ---
>  arch/x86/mm/Makefile               |  14 +-
>  arch/x86/mm/mem_encrypt.c          | 578 +----------------------------------
>  arch/x86/mm/mem_encrypt_identity.c | 596 +++++++++++++++++++++++++++++++++++++
>  arch/x86/mm/mm_internal.h          |   1 +
>  4 files changed, 607 insertions(+), 582 deletions(-)
>  create mode 100644 arch/x86/mm/mem_encrypt_identity.c
> 

...

> diff --git a/arch/x86/mm/mm_internal.h b/arch/x86/mm/mm_internal.h
> index 4e1f6e1b8159..7b4fc4386d90 100644
> --- a/arch/x86/mm/mm_internal.h
> +++ b/arch/x86/mm/mm_internal.h
> @@ -19,4 +19,5 @@ extern int after_bootmem;
>  
>  void update_cache_mode_entry(unsigned entry, enum page_cache_mode cache);
>  
> +extern bool sev_enabled __section(.data);

Lets move this into arch/x86/include/asm/mem_encrypt.h and then add
#include <linux/mem_encrypt.h> to mem_encrypt_identity.c.

Thanks,
Tom

>  #endif	/* __X86_MM_INTERNAL_H */
>