linux-kernel - Re: [PATCH] x86/mm: Decouple dynamic __PHYSICAL

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Date:   Fri, 20 Apr 2018 20:59:28 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>
Cc:     Tom Lendacky <thomas.lendacky@....com>,
        Dave Hansen <dave.hansen@...el.com>,
        Kai Huang <kai.huang@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] x86/mm: Decouple dynamic __PHYSICAL_MASK from AMD SME

On Tue, Apr 10, 2018 at 09:33:39AM +0000, Kirill A. Shutemov wrote:
> 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@...ux.intel.com>
> Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
> ---
> 
> Previously, I've posted the patch with MKTME patchset, but it's useful on
> its own as it reduces text size for kernel with AMD_MEM_ENCRYPT enabled.
> 
> Please consider applying.

Any feedback on this?

-- 
 Kirill A. Shutemov