arch/cc: Introduce a function to check for confidential computing features

commit 46b49b12f3fc5e1347dba37d4639e2165f447871 upstream.

In preparation 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() || ... ).

 [ bp: s/_CC_PLATFORM_H/_LINUX_CC_PLATFORM_H/g ]

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>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210928191009.32551-3-bp@alien8.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/Kconfig b/arch/Kconfig
index 8df1c71..d1e69d6 100644 (file)
--- 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 (file)
index 0000000..a075b70
--- /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 _LINUX_CC_PLATFORM_H
+#define _LINUX_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 /* _LINUX_CC_PLATFORM_H */