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

[Tom Lendacky]

On 1/30/2018 4:28 PM, Kirill A. Shutemov wrote:
> On Tue, Jan 30, 2018 at 04:26:03PM -0600, Tom Lendacky wrote:
>> 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@xxxxxxxxxxxxxxx>
>>
>> Just one minor comment at the end.  With that change:
>>
>> Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
>>
>>> ---
>>>  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.
> 
> Why? Will we need it beyond arch/x86/mm/ in the future?

I just think it would be best to keep all the memory encryption stuff
together.

Thanks,
Tom

>