linux-kernel - Re: [PATCH 1/3] x86/mm/encrypt: Move sme_populate

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Message-ID: <20180124103636.y5udfksagk2ndlzp@node.shutemov.name>
Date:   Wed, 24 Jan 2018 13:36:36 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Borislav Petkov <bp@...e.de>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] x86/mm/encrypt: Move sme_populate_pgd*() into
 separate translation unit

On Tue, Jan 23, 2018 at 08:19:08PM +0300, Kirill A. Shutemov wrote:
> sme_populate_pgd() and sme_populate_pgd_large() operate on the identity
> mapping, which means they want virtual addresses to be equal to physical
> one, without PAGE_OFFSET shift.
> 
> We also need to avoid paravirtualizaion call there.
> 
> Getting this done is tricky. We cannot use usual page table helpers.
> It forces us to open-code a lot of things. It makes code ugly and hard
> to modify.
> 
> We can get it work with the page table helpers, but it requires few
> preprocessor tricks. These tricks may have side effects for the rest of
> the file.
> 
> Let's isolate sme_populate_pgd() and sme_populate_pgd_large() into own
> translation unit.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> ---
>  arch/x86/mm/Makefile               |  13 ++--
>  arch/x86/mm/mem_encrypt.c          | 129 -----------------------------------
>  arch/x86/mm/mem_encrypt_identity.c | 134 +++++++++++++++++++++++++++++++++++++
>  arch/x86/mm/mm_internal.h          |  14 ++++
>  4 files changed, 156 insertions(+), 134 deletions(-)
>  create mode 100644 arch/x86/mm/mem_encrypt_identity.c
> 
> diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
> index 27e9e90a8d35..51e364ef12d9 100644
> --- a/arch/x86/mm/Makefile
> +++ b/arch/x86/mm/Makefile
> @@ -1,12 +1,14 @@
>  # SPDX-License-Identifier: GPL-2.0
> -# Kernel does not boot with instrumentation of tlb.c and mem_encrypt.c
> -KCOV_INSTRUMENT_tlb.o		:= n
> -KCOV_INSTRUMENT_mem_encrypt.o	:= n
> +# Kernel does not boot with instrumentation of tlb.c and mem_encrypt*.c
> +KCOV_INSTRUMENT_tlb.o			:= n
> +KCOV_INSTRUMENT_mem_encrypt.o		:= n
> +KCOV_INSTRUMENT_mem_encrypt_identity.o	:= n
>  
> -KASAN_SANITIZE_mem_encrypt.o	:= n
> +KASAN_SANITIZE_mem_encrypt.o		:= n
> +KASAN_SANITIZE_mem_encrypt_identity.o	:= n
>  
>  ifdef CONFIG_FUNCTION_TRACER
> -CFLAGS_REMOVE_mem_encrypt.o	= -pg
> +CFLAGS_REMOVE_mem_encrypt_identity.o	= -pg
>  endif

0day found a boot issue with the commit.

We need to add line on mem_encrypt_identity.o, not replace existing one.

Fixup is below.

diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index 51e364ef12d9..03c6c8561623 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -8,6 +8,7 @@ KASAN_SANITIZE_mem_encrypt.o		:= n
 KASAN_SANITIZE_mem_encrypt_identity.o	:= n
 
 ifdef CONFIG_FUNCTION_TRACER
+CFLAGS_REMOVE_mem_encrypt.o		= -pg
 CFLAGS_REMOVE_mem_encrypt_identity.o	= -pg
 endif
 
-- 
 Kirill A. Shutemov