[PATCH v3 2/8] mm: Introduce a function to check for confidential computing features

Tom Lendacky
2021-09-08T22:59:16Z

In prep for other confidential computing technologies, introduce a generic
helper function, cc_platform_has(), that can be used to check for specific
active confidential computing attributes, like memory encryption. This is
intended to eliminate having to add multiple technology-specific checks to
the code (e.g. if (sev_active() || tdx_active())).

Co-developed-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Co-developed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
arch/Kconfig | 3 ++
include/linux/cc_platform.h | 88 +++++++++++++++++++++++++++++++++++++
2 files changed, 91 insertions(+)
create mode 100644 include/linux/cc_platform.h

diff --git a/arch/Kconfig b/arch/Kconfig
index 3743174da870..ca7c359e5da8 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1234,6 +1234,9 @@ config RELR
config ARCH_HAS_MEM_ENCRYPT
bool

+config ARCH_HAS_CC_PLATFORM
+ bool
+
config HAVE_SPARSE_SYSCALL_NR
bool
help
diff --git a/include/linux/cc_platform.h b/include/linux/cc_platform.h
new file mode 100644
index 000000000000..253f3ea66cd8
--- /dev/null
+++ b/include/linux/cc_platform.h
@@ -0,0 +1,88 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Confidential Computing Platform Capability checks
+ *
+ * Copyright (C) 2021 Advanced Micro Devices, Inc.
+ *
+ * Author: Tom Lendacky <thomas.lendacky@amd.com>
+ */
+
+#ifndef _CC_PLATFORM_H
+#define _CC_PLATFORM_H
+
+#include <linux/types.h>
+#include <linux/stddef.h>
+
+/**
+ * enum cc_attr - Confidential computing attributes
+ *
+ * These attributes represent confidential computing features that are
+ * currently active.
+ */
+enum cc_attr {
+ /**
+ * @CC_ATTR_MEM_ENCRYPT: Memory encryption is active
+ *
+ * The platform/OS is running with active memory encryption. This
+ * includes running either as a bare-metal system or a hypervisor
+ * and actively using memory encryption or as a guest/virtual machine
+ * and actively using memory encryption.
+ *
+ * Examples include SME, SEV and SEV-ES.
+ */
+ CC_ATTR_MEM_ENCRYPT,
+
+ /**
+ * @CC_ATTR_HOST_MEM_ENCRYPT: Host memory encryption is active
+ *
+ * The platform/OS is running as a bare-metal system or a hypervisor
+ * and actively using memory encryption.
+ *
+ * Examples include SME.
+ */
+ CC_ATTR_HOST_MEM_ENCRYPT,
+
+ /**
+ * @CC_ATTR_GUEST_MEM_ENCRYPT: Guest memory encryption is active
+ *
+ * The platform/OS is running as a guest/virtual machine and actively
+ * using memory encryption.
+ *
+ * Examples include SEV and SEV-ES.
+ */
+ CC_ATTR_GUEST_MEM_ENCRYPT,
+
+ /**
+ * @CC_ATTR_GUEST_STATE_ENCRYPT: Guest state encryption is active
+ *
+ * The platform/OS is running as a guest/virtual machine and actively
+ * using memory encryption and register state encryption.
+ *
+ * Examples include SEV-ES.
+ */
+ CC_ATTR_GUEST_STATE_ENCRYPT,
+};
+
+#ifdef CONFIG_ARCH_HAS_CC_PLATFORM
+
+/**
+ * cc_platform_has() - Checks if the specified cc_attr attribute is active
+ * @attr: Confidential computing attribute to check
+ *
+ * The cc_platform_has() function will return an indicator as to whether the
+ * specified Confidential Computing attribute is currently active.
+ *
+ * Context: Any context
+ * Return:
+ * * TRUE - Specified Confidential Computing attribute is active
+ * * FALSE - Specified Confidential Computing attribute is not active
+ */
+bool cc_platform_has(enum cc_attr attr);
+
+#else /* !CONFIG_ARCH_HAS_CC_PLATFORM */
+
+static inline bool cc_platform_has(enum cc_attr attr) { return false; }
+
+#endif /* CONFIG_ARCH_HAS_CC_PLATFORM */
+
+#endif /* _CC_PLATFORM_H */
--
2.33.0