[tip: x86/urgent] x86/cc: Add cc_platform_set/_clear() helpers

[tip-bot2 for Borislav Petkov (AMD)]

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     bc6f707fc0feec72acc2f49c312eb31d257363a3
Gitweb:        https://git.kernel.org/tip/bc6f707fc0feec72acc2f49c312eb31d257363a3
Author:        Borislav Petkov (AMD) <bp@xxxxxxxxx>
AuthorDate:    Wed, 27 Mar 2024 16:43:16 +01:00
Committer:     Borislav Petkov (AMD) <bp@xxxxxxxxx>
CommitterDate: Thu, 04 Apr 2024 10:40:27 +02:00

x86/cc: Add cc_platform_set/_clear() helpers

Add functionality to set and/or clear different attributes of the
machine as a confidential computing platform. Add the first one too:
whether the machine is running as a host for SEV-SNP guests.

Fixes: 216d106c7ff7 ("x86/sev: Add SEV-SNP host initialization support")
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
Tested-by: Srikanth Aithal <sraithal@xxxxxxx>
Link: https://lore.kernel.org/r/20240327154317.29909-5-bp@xxxxxxxxx
---
 arch/x86/coco/core.c        | 52 ++++++++++++++++++++++++++++++++++++-
 include/linux/cc_platform.h | 12 ++++++++-
 2 files changed, 64 insertions(+)

diff --git a/arch/x86/coco/core.c b/arch/x86/coco/core.c
index ddd4efd..b31ef24 100644
--- a/arch/x86/coco/core.c
+++ b/arch/x86/coco/core.c
@@ -20,6 +20,11 @@
 enum cc_vendor cc_vendor __ro_after_init = CC_VENDOR_NONE;
 u64 cc_mask __ro_after_init;
 
+static struct cc_attr_flags {
+	__u64 host_sev_snp	: 1,
+	      __resv		: 63;
+} cc_flags;
+
 static bool noinstr intel_cc_platform_has(enum cc_attr attr)
 {
 	switch (attr) {
@@ -93,6 +98,9 @@ static bool noinstr amd_cc_platform_has(enum cc_attr attr)
 	case CC_ATTR_GUEST_SEV_SNP:
 		return sev_status & MSR_AMD64_SEV_SNP_ENABLED;
 
+	case CC_ATTR_HOST_SEV_SNP:
+		return cc_flags.host_sev_snp;
+
 	default:
 		return false;
 	}
@@ -153,6 +161,50 @@ u64 cc_mkdec(u64 val)
 }
 EXPORT_SYMBOL_GPL(cc_mkdec);
 
+static void amd_cc_platform_clear(enum cc_attr attr)
+{
+	switch (attr) {
+	case CC_ATTR_HOST_SEV_SNP:
+		cc_flags.host_sev_snp = 0;
+		break;
+	default:
+		break;
+	}
+}
+
+void cc_platform_clear(enum cc_attr attr)
+{
+	switch (cc_vendor) {
+	case CC_VENDOR_AMD:
+		amd_cc_platform_clear(attr);
+		break;
+	default:
+		break;
+	}
+}
+
+static void amd_cc_platform_set(enum cc_attr attr)
+{
+	switch (attr) {
+	case CC_ATTR_HOST_SEV_SNP:
+		cc_flags.host_sev_snp = 1;
+		break;
+	default:
+		break;
+	}
+}
+
+void cc_platform_set(enum cc_attr attr)
+{
+	switch (cc_vendor) {
+	case CC_VENDOR_AMD:
+		amd_cc_platform_set(attr);
+		break;
+	default:
+		break;
+	}
+}
+
 __init void cc_random_init(void)
 {
 	/*
diff --git a/include/linux/cc_platform.h b/include/linux/cc_platform.h
index cb0d6cd..60693a1 100644
--- a/include/linux/cc_platform.h
+++ b/include/linux/cc_platform.h
@@ -90,6 +90,14 @@ enum cc_attr {
 	 * Examples include TDX Guest.
 	 */
 	CC_ATTR_HOTPLUG_DISABLED,
+
+	/**
+	 * @CC_ATTR_HOST_SEV_SNP: AMD SNP enabled on the host.
+	 *
+	 * The host kernel is running with the necessary features
+	 * enabled to run SEV-SNP guests.
+	 */
+	CC_ATTR_HOST_SEV_SNP,
 };
 
 #ifdef CONFIG_ARCH_HAS_CC_PLATFORM
@@ -107,10 +115,14 @@ enum cc_attr {
  * * FALSE - Specified Confidential Computing attribute is not active
  */
 bool cc_platform_has(enum cc_attr attr);
+void cc_platform_set(enum cc_attr attr);
+void cc_platform_clear(enum cc_attr attr);
 
 #else	/* !CONFIG_ARCH_HAS_CC_PLATFORM */
 
 static inline bool cc_platform_has(enum cc_attr attr) { return false; }
+static inline void cc_platform_set(enum cc_attr attr) { }
+static inline void cc_platform_clear(enum cc_attr attr) { }
 
 #endif	/* CONFIG_ARCH_HAS_CC_PLATFORM */