Re: [PATCH v5 09/32] x86/mm: Provide general kernel support for memory encryption

Tom Lendacky
2017-05-04T14:34:37Z

On 4/27/2017 11:12 AM, Borislav Petkov wrote:
> On Tue, Apr 18, 2017 at 04:17:54PM -0500, Tom Lendacky wrote:
>> Changes to the existing page table macros will allow the SME support to
>> be enabled in a simple fashion with minimal changes to files that use these
>> macros. Since the memory encryption mask will now be part of the regular
>> pagetable macros, we introduce two new macros (_PAGE_TABLE_NOENC and
>> _KERNPG_TABLE_NOENC) to allow for early pagetable creation/initialization
>> without the encryption mask before SME becomes active. Two new pgprot()
>> macros are defined to allow setting or clearing the page encryption mask.
>
> ...
>
>> @@ -55,7 +57,7 @@ static inline void copy_user_page(void *to, void *from, unsigned long vaddr,
>> __phys_addr_symbol(__phys_reloc_hide((unsigned long)(x)))
>>
>> #ifndef __va
>> -#define __va(x) ((void *)((unsigned long)(x)+PAGE_OFFSET))
>> +#define __va(x) ((void *)(__sme_clr(x) + PAGE_OFFSET))
>> #endif
>>
>> #define __boot_va(x) __va(x)
>> diff --git a/arch/x86/include/asm/page_types.h b/arch/x86/include/asm/page_types.h
>> index 7bd0099..fead0a5 100644
>> --- a/arch/x86/include/asm/page_types.h
>> +++ b/arch/x86/include/asm/page_types.h
>> @@ -15,7 +15,7 @@
>> #define PUD_PAGE_SIZE (_AC(1, UL) << PUD_SHIFT)
>> #define PUD_PAGE_MASK (~(PUD_PAGE_SIZE-1))
>>
>> -#define __PHYSICAL_MASK ((phys_addr_t)((1ULL << __PHYSICAL_MASK_SHIFT) - 1))
>> +#define __PHYSICAL_MASK ((phys_addr_t)(__sme_clr((1ULL << __PHYSICAL_MASK_SHIFT) - 1)))
>
> That looks strange: poking SME mask hole into a mask...?

I masked it out here based on a previous comment from Dave Hansen:

http://marc.info/?l=linux-kernel&m=148778719826905&w=2

I could move the __sme_clr into the individual defines of:

PHYSICAL_PAGE_MASK, PHYSICAL_PMD_PAGE_MASK and PHYSICAL_PUD_PAGE_MASK

Either way works for me.

Thanks,
Tom

>
>> #define __VIRTUAL_MASK ((1UL << __VIRTUAL_MASK_SHIFT) - 1)
>>
>> /* Cast *PAGE_MASK to a signed type so that it is sign-extended if
>