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Date: Mon, 14 Nov 2016 18:29:30 +0100
From: Borislav Petkov <bp@...en8.de>
To: Tom Lendacky <thomas.lendacky@....com>
Cc: linux-arch@...r.kernel.org, linux-efi@...r.kernel.org,
kvm@...r.kernel.org, linux-doc@...r.kernel.org, x86@...nel.org,
linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
linux-mm@...ck.org, iommu@...ts.linux-foundation.org,
Rik van Riel <riel@...hat.com>,
Radim Krčmář <rkrcmar@...hat.com>,
Arnd Bergmann <arnd@...db.de>,
Jonathan Corbet <corbet@....net>,
Matt Fleming <matt@...eblueprint.co.uk>,
Joerg Roedel <joro@...tes.org>,
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Larry Woodman <lwoodman@...hat.com>,
Ingo Molnar <mingo@...hat.com>,
Andy Lutomirski <luto@...nel.org>,
"H. Peter Anvin" <hpa@...or.com>,
Andrey Ryabinin <aryabinin@...tuozzo.com>,
Alexander Potapenko <glider@...gle.com>,
Thomas Gleixner <tglx@...utronix.de>,
Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [RFC PATCH v3 06/20] x86: Add support to enable SME during early
boot processing
On Wed, Nov 09, 2016 at 06:35:43PM -0600, Tom Lendacky wrote:
> This patch adds support to the early boot code to use Secure Memory
> Encryption (SME). Support is added to update the early pagetables with
> the memory encryption mask and to encrypt the kernel in place.
>
> The routines to set the encryption mask and perform the encryption are
> stub routines for now with full function to be added in a later patch.
>
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
> ---
> arch/x86/kernel/Makefile | 2 ++
> arch/x86/kernel/head_64.S | 35 ++++++++++++++++++++++++++++++++++-
> arch/x86/kernel/mem_encrypt_init.c | 29 +++++++++++++++++++++++++++++
> 3 files changed, 65 insertions(+), 1 deletion(-)
> create mode 100644 arch/x86/kernel/mem_encrypt_init.c
>
> diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
> index 45257cf..27e22f4 100644
> --- a/arch/x86/kernel/Makefile
> +++ b/arch/x86/kernel/Makefile
> @@ -141,4 +141,6 @@ ifeq ($(CONFIG_X86_64),y)
>
> obj-$(CONFIG_PCI_MMCONFIG) += mmconf-fam10h_64.o
> obj-y += vsmp_64.o
> +
> + obj-y += mem_encrypt_init.o
> endif
> diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
> index c98a559..9a28aad 100644
> --- a/arch/x86/kernel/head_64.S
> +++ b/arch/x86/kernel/head_64.S
> @@ -95,6 +95,17 @@ startup_64:
> jnz bad_address
>
> /*
> + * Enable Secure Memory Encryption (if available). Save the mask
> + * in %r12 for later use and add the memory encryption mask to %rbp
> + * to include it in the page table fixups.
> + */
> + push %rsi
> + call sme_enable
> + pop %rsi
Why %rsi?
sme_enable() is void so no args in registers and returns in %rax.
/me is confused.
> + movq %rax, %r12
> + addq %r12, %rbp
> +
> + /*
> * Fixup the physical addresses in the page table
> */
> addq %rbp, early_level4_pgt + (L4_START_KERNEL*8)(%rip)
> @@ -117,6 +128,7 @@ startup_64:
> shrq $PGDIR_SHIFT, %rax
>
> leaq (4096 + _KERNPG_TABLE)(%rbx), %rdx
> + addq %r12, %rdx
> movq %rdx, 0(%rbx,%rax,8)
> movq %rdx, 8(%rbx,%rax,8)
>
> @@ -133,6 +145,7 @@ startup_64:
> movq %rdi, %rax
> shrq $PMD_SHIFT, %rdi
> addq $(__PAGE_KERNEL_LARGE_EXEC & ~_PAGE_GLOBAL), %rax
> + addq %r12, %rax
> leaq (_end - 1)(%rip), %rcx
> shrq $PMD_SHIFT, %rcx
> subq %rdi, %rcx
> @@ -163,9 +176,21 @@ startup_64:
> cmp %r8, %rdi
> jne 1b
>
> - /* Fixup phys_base */
> + /*
> + * Fixup phys_base, remove the memory encryption mask from %rbp
> + * to obtain the true physical address.
> + */
> + subq %r12, %rbp
> addq %rbp, phys_base(%rip)
>
> + /*
> + * The page tables have been updated with the memory encryption mask,
> + * so encrypt the kernel if memory encryption is active
> + */
> + push %rsi
> + call sme_encrypt_kernel
> + pop %rsi
Ditto.
> +
> movq $(early_level4_pgt - __START_KERNEL_map), %rax
> jmp 1f
> ENTRY(secondary_startup_64)
> @@ -186,9 +211,17 @@ ENTRY(secondary_startup_64)
> /* Sanitize CPU configuration */
> call verify_cpu
>
> + push %rsi
> + call sme_get_me_mask
> + pop %rsi
Ditto.
> + movq %rax, %r12
> +
> movq $(init_level4_pgt - __START_KERNEL_map), %rax
> 1:
>
> + /* Add the memory encryption mask to RAX */
I think that should say something like:
/*
* Add the memory encryption mask to init_level4_pgt's physical address
*/
or so...
> + addq %r12, %rax
> +
> /* Enable PAE mode and PGE */
> movl $(X86_CR4_PAE | X86_CR4_PGE), %ecx
> movq %rcx, %cr4
> diff --git a/arch/x86/kernel/mem_encrypt_init.c b/arch/x86/kernel/mem_encrypt_init.c
> new file mode 100644
> index 0000000..388d6fb
> --- /dev/null
> +++ b/arch/x86/kernel/mem_encrypt_init.c
So nothing in the commit message explains why we need a separate
mem_encrypt_init.c file when we already have arch/x86/mm/mem_encrypt.c
for all memory encryption code...
> @@ -0,0 +1,29 @@
> +/*
> + * AMD Memory Encryption Support
> + *
> + * Copyright (C) 2016 Advanced Micro Devices, Inc.
> + *
> + * Author: Tom Lendacky <thomas.lendacky@....com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/linkage.h>
> +#include <linux/init.h>
> +#include <linux/mem_encrypt.h>
> +
> +void __init sme_encrypt_kernel(void)
> +{
> +}
> +
> +unsigned long __init sme_get_me_mask(void)
> +{
> + return sme_me_mask;
> +}
> +
> +unsigned long __init sme_enable(void)
> +{
> + return sme_me_mask;
> +}
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
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