[PATCH 4/5] x86/cc: Add cc_platform_set/_clear() helpers

Borislav Petkov
2024-03-27T15:44:17Z

From: "Borislav Petkov (AMD)" <bp@alien8.de>

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.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
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 d07be9d05cd0..8c3fae23d3c6 100644
--- a/arch/x86/coco/core.c
+++ b/arch/x86/coco/core.c
@@ -16,6 +16,11 @@
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) {
@@ -89,6 +94,9 @@ 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;
}
@@ -148,3 +156,47 @@ 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;
+ }
+}
diff --git a/include/linux/cc_platform.h b/include/linux/cc_platform.h
index cb0d6cd1c12f..60693a145894 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 */

--
2.43.0