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Date: Mon, 12 Sep 2016 19:08:56 +0200
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,
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>,
Andrey Ryabinin <aryabinin@...tuozzo.com>,
Ingo Molnar <mingo@...hat.com>,
Andy Lutomirski <luto@...nel.org>,
"H. Peter Anvin" <hpa@...or.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Alexander Potapenko <glider@...gle.com>,
Thomas Gleixner <tglx@...utronix.de>,
Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [RFC PATCH v2 20/20] x86: Add support to make use of Secure
Memory Encryption
On Mon, Aug 22, 2016 at 05:39:08PM -0500, Tom Lendacky wrote:
> This patch adds the support to check if SME has been enabled and if the
> mem_encrypt=on command line option is set. If both of these conditions
> are true, then the encryption mask is set and the kernel is encrypted
> "in place."
>
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
> ---
> Documentation/kernel-parameters.txt | 3
> arch/x86/kernel/asm-offsets.c | 2
> arch/x86/kernel/mem_encrypt.S | 302 +++++++++++++++++++++++++++++++++++
> arch/x86/mm/mem_encrypt.c | 2
> 4 files changed, 309 insertions(+)
>
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index 46c030a..a1986c8 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -2268,6 +2268,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
> memory contents and reserves bad memory
> regions that are detected.
>
> + mem_encrypt=on [X86_64] Enable memory encryption on processors
> + that support this feature.
> +
> meye.*= [HW] Set MotionEye Camera parameters
> See Documentation/video4linux/meye.txt.
>
> diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
> index 2bd5c6f..e485ada 100644
> --- a/arch/x86/kernel/asm-offsets.c
> +++ b/arch/x86/kernel/asm-offsets.c
> @@ -85,6 +85,8 @@ void common(void) {
> OFFSET(BP_init_size, boot_params, hdr.init_size);
> OFFSET(BP_pref_address, boot_params, hdr.pref_address);
> OFFSET(BP_code32_start, boot_params, hdr.code32_start);
> + OFFSET(BP_cmd_line_ptr, boot_params, hdr.cmd_line_ptr);
> + OFFSET(BP_ext_cmd_line_ptr, boot_params, ext_cmd_line_ptr);
>
> BLANK();
> DEFINE(PTREGS_SIZE, sizeof(struct pt_regs));
> diff --git a/arch/x86/kernel/mem_encrypt.S b/arch/x86/kernel/mem_encrypt.S
> index f2e0536..bf9f6a9 100644
> --- a/arch/x86/kernel/mem_encrypt.S
> +++ b/arch/x86/kernel/mem_encrypt.S
> @@ -12,13 +12,230 @@
>
> #include <linux/linkage.h>
>
> +#include <asm/processor-flags.h>
> +#include <asm/pgtable.h>
> +#include <asm/page.h>
> +#include <asm/msr.h>
> +#include <asm/asm-offsets.h>
> +
> .text
> .code64
> ENTRY(sme_enable)
> +#ifdef CONFIG_AMD_MEM_ENCRYPT
> + /* Check for AMD processor */
> + xorl %eax, %eax
> + cpuid
> + cmpl $0x68747541, %ebx # AuthenticAMD
> + jne .Lmem_encrypt_exit
> + cmpl $0x69746e65, %edx
> + jne .Lmem_encrypt_exit
> + cmpl $0x444d4163, %ecx
> + jne .Lmem_encrypt_exit
> +
> + /* Check for memory encryption leaf */
> + movl $0x80000000, %eax
> + cpuid
> + cmpl $0x8000001f, %eax
> + jb .Lmem_encrypt_exit
> +
> + /*
> + * Check for memory encryption feature:
> + * CPUID Fn8000_001F[EAX] - Bit 0
> + * Secure Memory Encryption support
> + * CPUID Fn8000_001F[EBX] - Bits 5:0
> + * Pagetable bit position used to indicate encryption
> + * CPUID Fn8000_001F[EBX] - Bits 11:6
> + * Reduction in physical address space (in bits) when enabled
> + */
> + movl $0x8000001f, %eax
> + cpuid
> + bt $0, %eax
> + jnc .Lmem_encrypt_exit
> +
> + /* Check if BIOS/UEFI has allowed memory encryption */
> + movl $MSR_K8_SYSCFG, %ecx
> + rdmsr
> + bt $MSR_K8_SYSCFG_MEM_ENCRYPT_BIT, %eax
> + jnc .Lmem_encrypt_exit
Like other people suggested, it would be great if this were in C. Should be
actually readable :)
> +
> + /* Check for the mem_encrypt=on command line option */
> + push %rsi /* Save RSI (real_mode_data) */
> + push %rbx /* Save CPUID information */
> + movl BP_ext_cmd_line_ptr(%rsi), %ecx
> + shlq $32, %rcx
> + movl BP_cmd_line_ptr(%rsi), %edi
> + addq %rcx, %rdi
> + leaq mem_encrypt_enable_option(%rip), %rsi
> + call cmdline_find_option_bool
> + pop %rbx /* Restore CPUID information */
> + pop %rsi /* Restore RSI (real_mode_data) */
> + testl %eax, %eax
> + jz .Lno_mem_encrypt
This too.
> +
> + /* Set memory encryption mask */
> + movl %ebx, %ecx
> + andl $0x3f, %ecx
> + bts %ecx, sme_me_mask(%rip)
> +
> +.Lno_mem_encrypt:
> + /*
> + * BIOS/UEFI has allowed memory encryption so we need to set
> + * the amount of physical address space reduction even if
> + * the user decides not to use memory encryption.
> + */
> + movl %ebx, %ecx
> + shrl $6, %ecx
> + andl $0x3f, %ecx
> + movb %cl, sme_me_loss(%rip)
> +
> +.Lmem_encrypt_exit:
> +#endif /* CONFIG_AMD_MEM_ENCRYPT */
> +
> ret
> ENDPROC(sme_enable)
>
> ENTRY(sme_encrypt_kernel)
This should be doable too but I guess you'll have to try it to see.
...
> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
> index 2f28d87..1154353 100644
> --- a/arch/x86/mm/mem_encrypt.c
> +++ b/arch/x86/mm/mem_encrypt.c
> @@ -183,6 +183,8 @@ void __init mem_encrypt_init(void)
>
> /* Make SWIOTLB use an unencrypted DMA area */
> swiotlb_clear_encryption();
> +
> + pr_info("memory encryption active\n");
Let's make it more official with nice caps and so on...
pr_info("AMD Secure Memory Encryption active.\n");
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
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