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

From: Tom Lendacky
Date: Thu May 04 2017 - 11:12:43 EST

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))

#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 __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:

I could move the __sme_clr into the individual defines of:


Either way works for me.


#define __VIRTUAL_MASK ((1UL << __VIRTUAL_MASK_SHIFT) - 1)

/* Cast *PAGE_MASK to a signed type so that it is sign-extended if