1 files changed, 103 insertions, 1 deletions

diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index 2de01b379aa3..dc73194416ac 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -5,6 +5,7 @@
 #include <linux/freezer.h>
 #include <linux/highmem.h>
 #include <linux/kthread.h>
+#include <linux/kvm_types.h>
 #include <linux/miscdevice.h>
 #include <linux/node.h>
 #include <linux/pagemap.h>
@@ -16,6 +17,7 @@
 #include <linux/vmalloc.h>
 #include <asm/msr.h>
 #include <asm/sgx.h>
+#include <asm/archrandom.h>
 #include "driver.h"
 #include "encl.h"
 #include "encls.h"
@@ -915,7 +917,107 @@ int sgx_set_attribute(unsigned long *allowed_attributes,
 	*allowed_attributes |= SGX_ATTR_PROVISIONKEY;
 	return 0;
 }
-EXPORT_SYMBOL_GPL(sgx_set_attribute);
+EXPORT_SYMBOL_FOR_KVM(sgx_set_attribute);
+
+/* Counter to count the active SGX users */
+static int sgx_usage_count;
+
+/**
+ * sgx_update_svn() - Attempt to call ENCLS[EUPDATESVN].
+ *
+ * This instruction attempts to update CPUSVN to the
+ * currently loaded microcode update SVN and generate new
+ * cryptographic assets.
+ *
+ * Return:
+ * * %0:       - Success or not supported
+ * * %-EAGAIN: - Can be safely retried, failure is due to lack of
+ * *             entropy in RNG
+ * * %-EIO:    - Unexpected error, retries are not advisable
+ */
+static int sgx_update_svn(void)
+{
+	int ret;
+
+	/*
+	 * If EUPDATESVN is not available, it is ok to
+	 * silently skip it to comply with legacy behavior.
+	 */
+	if (!cpu_feature_enabled(X86_FEATURE_SGX_EUPDATESVN))
+		return 0;
+
+	/*
+	 * EPC is guaranteed to be empty when there are no users.
+	 * Ensure we are on our first user before proceeding further.
+	 */
+	WARN(sgx_usage_count, "Elevated usage count when calling EUPDATESVN\n");
+
+	for (int i = 0; i < RDRAND_RETRY_LOOPS; i++) {
+		ret = __eupdatesvn();
+
+		/* Stop on success or unexpected errors: */
+		if (ret != SGX_INSUFFICIENT_ENTROPY)
+			break;
+	}
+
+	switch (ret) {
+	case 0:
+		/*
+		 * SVN successfully updated.
+		 * Let users know when the update was successful.
+		 */
+		pr_info("SVN updated successfully\n");
+		return 0;
+	case SGX_NO_UPDATE:
+		/*
+		 * SVN update failed since the current SVN is
+		 * not newer than CPUSVN. This is the most
+		 * common case and indicates no harm.
+		 */
+		return 0;
+	case SGX_INSUFFICIENT_ENTROPY:
+		/*
+		 * SVN update failed due to lack of entropy in DRNG.
+		 * Indicate to userspace that it should retry.
+		 */
+		return -EAGAIN;
+	default:
+		break;
+	}
+
+	/*
+	 * EUPDATESVN was called when EPC is empty, all other error
+	 * codes are unexpected.
+	 */
+	ENCLS_WARN(ret, "EUPDATESVN");
+	return -EIO;
+}
+
+/* Mutex to ensure no concurrent EPC accesses during EUPDATESVN */
+static DEFINE_MUTEX(sgx_svn_lock);
+
+int sgx_inc_usage_count(void)
+{
+	int ret;
+
+	guard(mutex)(&sgx_svn_lock);
+
+	if (!sgx_usage_count) {
+		ret = sgx_update_svn();
+		if (ret)
+			return ret;
+	}
+
+	sgx_usage_count++;
+
+	return 0;
+}
+
+void sgx_dec_usage_count(void)
+{
+	guard(mutex)(&sgx_svn_lock);
+	sgx_usage_count--;
+}
 
 static int __init sgx_init(void)
 {