[Xen-devel] [PATCH v7 06/36] x86/mm: Add Secure Memory Encryption (SME) support

[Tom Lendacky <thomas.lendacky@xxxxxxx>]

Add support for Secure Memory Encryption (SME). This initial support
provides a Kconfig entry to build the SME support into the kernel and
defines the memory encryption mask that will be used in subsequent
patches to mark pages as encrypted.

Reviewed-by: Borislav Petkov <bp@xxxxxxx>
Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
---
 arch/x86/Kconfig                   |   26 ++++++++++++++++++++++++++
 arch/x86/include/asm/mem_encrypt.h |   30 ++++++++++++++++++++++++++++++
 arch/x86/mm/Makefile               |    1 +
 arch/x86/mm/mem_encrypt.c          |   21 +++++++++++++++++++++
 include/linux/mem_encrypt.h        |   35 +++++++++++++++++++++++++++++++++++
 5 files changed, 113 insertions(+)
 create mode 100644 arch/x86/include/asm/mem_encrypt.h
 create mode 100644 arch/x86/mm/mem_encrypt.c
 create mode 100644 include/linux/mem_encrypt.h

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 7c991d0..cf74791 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1407,6 +1407,32 @@ config X86_DIRECT_GBPAGES
          supports them), so don't confuse the user by printing
          that we have them enabled.
 
+config ARCH_HAS_MEM_ENCRYPT
+       def_bool y
+       depends on X86
+
+config AMD_MEM_ENCRYPT
+       bool "AMD Secure Memory Encryption (SME) support"
+       depends on X86_64 && CPU_SUP_AMD
+       ---help---
+         Say yes to enable support for the encryption of system memory.
+         This requires an AMD processor that supports Secure Memory
+         Encryption (SME).
+
+config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
+       bool "Activate AMD Secure Memory Encryption (SME) by default"
+       default y
+       depends on AMD_MEM_ENCRYPT
+       ---help---
+         Say yes to have system memory encrypted by default if running on
+         an AMD processor that supports Secure Memory Encryption (SME).
+
+         If set to Y, then the encryption of system memory can be
+         deactivated with the mem_encrypt=off command line option.
+
+         If set to N, then the encryption of system memory can be
+         activated with the mem_encrypt=on command line option.
+
 # Common NUMA Features
 config NUMA
        bool "Numa Memory Allocation and Scheduler Support"
diff --git a/arch/x86/include/asm/mem_encrypt.h 
b/arch/x86/include/asm/mem_encrypt.h
new file mode 100644
index 0000000..a105796
--- /dev/null
+++ b/arch/x86/include/asm/mem_encrypt.h
@@ -0,0 +1,30 @@
+/*
+ * AMD Memory Encryption Support
+ *
+ * Copyright (C) 2016 Advanced Micro Devices, Inc.
+ *
+ * Author: Tom Lendacky <thomas.lendacky@xxxxxxx>
+ *
+ * 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.
+ */
+
+#ifndef __X86_MEM_ENCRYPT_H__
+#define __X86_MEM_ENCRYPT_H__
+
+#ifndef __ASSEMBLY__
+
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+
+extern unsigned long sme_me_mask;
+
+#else  /* !CONFIG_AMD_MEM_ENCRYPT */
+
+#define sme_me_mask    0UL
+
+#endif /* CONFIG_AMD_MEM_ENCRYPT */
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* __X86_MEM_ENCRYPT_H__ */
diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index 0fbdcb6..a94a7b6 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -39,3 +39,4 @@ obj-$(CONFIG_X86_INTEL_MPX)   += mpx.o
 obj-$(CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS) += pkeys.o
 obj-$(CONFIG_RANDOMIZE_MEMORY) += kaslr.o
 
+obj-$(CONFIG_AMD_MEM_ENCRYPT)  += mem_encrypt.o
diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
new file mode 100644
index 0000000..b99d469
--- /dev/null
+++ b/arch/x86/mm/mem_encrypt.c
@@ -0,0 +1,21 @@
+/*
+ * AMD Memory Encryption Support
+ *
+ * Copyright (C) 2016 Advanced Micro Devices, Inc.
+ *
+ * Author: Tom Lendacky <thomas.lendacky@xxxxxxx>
+ *
+ * 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>
+
+/*
+ * Since SME related variables are set early in the boot process they must
+ * reside in the .data section so as not to be zeroed out when the .bss
+ * section is later cleared.
+ */
+unsigned long sme_me_mask __section(.data) = 0;
+EXPORT_SYMBOL_GPL(sme_me_mask);
diff --git a/include/linux/mem_encrypt.h b/include/linux/mem_encrypt.h
new file mode 100644
index 0000000..59769f7
--- /dev/null
+++ b/include/linux/mem_encrypt.h
@@ -0,0 +1,35 @@
+/*
+ * AMD Memory Encryption Support
+ *
+ * Copyright (C) 2016 Advanced Micro Devices, Inc.
+ *
+ * Author: Tom Lendacky <thomas.lendacky@xxxxxxx>
+ *
+ * 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.
+ */
+
+#ifndef __MEM_ENCRYPT_H__
+#define __MEM_ENCRYPT_H__
+
+#ifndef __ASSEMBLY__
+
+#ifdef CONFIG_ARCH_HAS_MEM_ENCRYPT
+
+#include <asm/mem_encrypt.h>
+
+#else  /* !CONFIG_ARCH_HAS_MEM_ENCRYPT */
+
+#define sme_me_mask    0UL
+
+#endif /* CONFIG_ARCH_HAS_MEM_ENCRYPT */
+
+static inline bool sme_active(void)
+{
+       return !!sme_me_mask;
+}
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* __MEM_ENCRYPT_H__ */


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