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Date: Wed, 14 Sep 2016 09:31:42 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: Borislav Petkov <bp@...en8.de>
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 09/12/2016 12:08 PM, Borislav Petkov wrote:
> 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 :)
Yup, working on that. I'll try and make it all completely C.
>
>> +
>> + /* 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");
Will do.
Thanks,
Tom
>
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