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
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index ffc8c13..3ca59cf 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -8,6 +8,11 @@
#include <asm/fixmap.h>
#include <asm/mtrr.h>
+#ifdef CONFIG_DYNAMIC_PHYSICAL_MASK
+phys_addr_t physical_mask __ro_after_init = (1ULL << __PHYSICAL_MASK_SHIFT) - 1;
+EXPORT_SYMBOL(physical_mask);
+#endif
+
#define PGALLOC_GFP (GFP_KERNEL_ACCOUNT | __GFP_ZERO)
#ifdef CONFIG_HIGHPTE