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x86/mm: Decouple dynamic __PHYSICAL_MASK from AMD SME

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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
This commit is contained in:
Kirill A. Shutemov
2018-05-18 14:30:28 +03:00
committed by Thomas Gleixner
parent 046c0dbec0
commit 94d49eb30e
5 changed files with 24 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
arch/x86/mm/mem_encrypt_identity.c
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@@ -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;
}