x86/mm: Decouple dynamic __PHYSICAL_MASK from AMD SME

AMD SME claims one bit from physical address to indicate whether the
page is encrypted or not. To achieve that we clear out the bit from
__PHYSICAL_MASK.

The capability to adjust __PHYSICAL_MASK is required beyond AMD SME.
For instance for upcoming Intel Multi-Key Total Memory Encryption.

Factor it out into a separate feature with own Kconfig handle.

It also helps with overhead of AMD SME. It saves more than 3k in .text
on defconfig + AMD_MEM_ENCRYPT:

	add/remove: 3/2 grow/shrink: 5/110 up/down: 189/-3753 (-3564)

We would need to return to this once we have infrastructure to patch
constants in code. That's good candidate for it.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Cc: linux-mm@kvack.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lkml.kernel.org/r/20180518113028.79825-1-kirill.shutemov@linux.intel.com

1 files changed, 3 insertions, 0 deletions

diff --git a/arch/x86/mm/mem_encrypt_identity.c b/arch/x86/mm/mem_encrypt_identity.c
index 1b2197d13832..7ae36868aed2 100644
--- a/arch/x86/mm/mem_encrypt_identity.c
+++ b/arch/x86/mm/mem_encrypt_identity.c
@@ -527,6 +527,7 @@ void __init sme_enable(struct boot_params *bp)
 		/* SEV state cannot be controlled by a command line option */
 		sme_me_mask = me_mask;
 		sev_enabled = true;
+		physical_mask &= ~sme_me_mask;
 		return;
 	}
 
@@ -561,4 +562,6 @@ void __init sme_enable(struct boot_params *bp)
 		sme_me_mask = 0;
 	else
 		sme_me_mask = active_by_default ? me_mask : 0;
+
+	physical_mask &= ~sme_me_mask;
 }