[svsm-devel] [PATCH v3 13/14] x86/sev: Hide SVSM attestation entries if not running under an SVSM

[Tom Lendacky]

Config-fs provides support to hide individual attribute entries. Using
this support, base the display of the SVSM related entries on the presence
of an SVSM.

Cc: Joel Becker <jlbec at evilplan.org>
Cc: Christoph Hellwig <hch at lst.de>
Signed-off-by: Tom Lendacky <thomas.lendacky at amd.com>
---
 arch/x86/coco/core.c        |  4 ++++
 drivers/virt/coco/tsm.c     | 14 ++++++++++----
 include/linux/cc_platform.h |  8 ++++++++
 3 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/arch/x86/coco/core.c b/arch/x86/coco/core.c
index d07be9d05cd0..efa0f648f754 100644
--- a/arch/x86/coco/core.c
+++ b/arch/x86/coco/core.c
@@ -12,6 +12,7 @@
 
 #include <asm/coco.h>
 #include <asm/processor.h>
+#include <asm/sev.h>
 
 enum cc_vendor cc_vendor __ro_after_init = CC_VENDOR_NONE;
 u64 cc_mask __ro_after_init;
@@ -78,6 +79,9 @@ static bool noinstr amd_cc_platform_has(enum cc_attr attr)
 	case CC_ATTR_GUEST_STATE_ENCRYPT:
 		return sev_status & MSR_AMD64_SEV_ES_ENABLED;
 
+	case CC_ATTR_GUEST_SVSM_PRESENT:
+		return snp_get_vmpl();
+
 	/*
 	 * With SEV, the rep string I/O instructions need to be unrolled
 	 * but SEV-ES supports them through the #VC handler.
diff --git a/drivers/virt/coco/tsm.c b/drivers/virt/coco/tsm.c
index 46f230bf13ac..d30471874e87 100644
--- a/drivers/virt/coco/tsm.c
+++ b/drivers/virt/coco/tsm.c
@@ -64,6 +64,12 @@ static struct tsm_report_state *to_state(struct tsm_report *report)
 	return container_of(report, struct tsm_report_state, report);
 }
 
+static bool provider_visibility(const struct config_item *item,
+				const struct configfs_attribute *attr)
+{
+	return cc_platform_has(CC_ATTR_GUEST_SVSM_PRESENT);
+}
+
 static int try_advance_write_generation(struct tsm_report *report)
 {
 	struct tsm_report_state *state = to_state(report);
@@ -144,7 +150,7 @@ static ssize_t tsm_report_service_provider_store(struct config_item *cfg,
 
 	return len;
 }
-CONFIGFS_ATTR_WO(tsm_report_, service_provider);
+CONFIGFS_ATTR_VISIBLE_WO(tsm_report_, service_provider, provider_visibility);
 
 static ssize_t tsm_report_service_guid_store(struct config_item *cfg,
 					     const char *buf, size_t len)
@@ -165,7 +171,7 @@ static ssize_t tsm_report_service_guid_store(struct config_item *cfg,
 
 	return len;
 }
-CONFIGFS_ATTR_WO(tsm_report_, service_guid);
+CONFIGFS_ATTR_VISIBLE_WO(tsm_report_, service_guid, provider_visibility);
 
 static ssize_t tsm_report_service_manifest_version_store(struct config_item *cfg,
 							 const char *buf, size_t len)
@@ -186,7 +192,7 @@ static ssize_t tsm_report_service_manifest_version_store(struct config_item *cfg
 
 	return len;
 }
-CONFIGFS_ATTR_WO(tsm_report_, service_manifest_version);
+CONFIGFS_ATTR_VISIBLE_WO(tsm_report_, service_manifest_version, provider_visibility);
 
 static ssize_t tsm_report_inblob_write(struct config_item *cfg,
 				       const void *buf, size_t count)
@@ -333,7 +339,7 @@ static ssize_t tsm_report_manifestblob_read(struct config_item *cfg, void *buf,
 
 	return tsm_report_read(report, buf, count, TSM_MANIFEST);
 }
-CONFIGFS_BIN_ATTR_RO(tsm_report_, manifestblob, NULL, TSM_OUTBLOB_MAX);
+CONFIGFS_BIN_ATTR_VISIBLE_RO(tsm_report_, manifestblob, NULL, TSM_OUTBLOB_MAX, provider_visibility);
 
 #define TSM_DEFAULT_ATTRS() \
 	&tsm_report_attr_generation, \
diff --git a/include/linux/cc_platform.h b/include/linux/cc_platform.h
index cb0d6cd1c12f..f1b4266c1484 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_GUEST_SVSM_PRESENT: Guest is running under an SVSM
+	 *
+	 * The platform/OS is running as a guest/virtual machine and is
+	 * running under a Secure VM Service Module (SVSM).
+	 */
+	CC_ATTR_GUEST_SVSM_PRESENT,
 };
 
 #ifdef CONFIG_ARCH_HAS_CC_PLATFORM
-- 
2.43.2