[PATCH v13 10/13] x86/sgx: Add sgx_einit() for initializing enclaves

[Jarkko Sakkinen]

From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>

Add a function to perform ENCLS(EINIT), which initializes an enclave,
which can be used by a driver for running enclaves and VMMs.

Writing the LE hash MSRs is extraordinarily expensive, e.g. 3-4x slower
than normal MSRs, so we use a per-cpu cache to track the last known value
of the MSRs to avoid unnecessarily writing the MSRs with the current value.

Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Co-developed-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
---
 arch/x86/include/asm/sgx.h      |  2 +
 arch/x86/kernel/cpu/intel_sgx.c | 86 +++++++++++++++++++++++++++++++--
 2 files changed, 85 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/sgx.h b/arch/x86/include/asm/sgx.h
index baf30d49b71f..c15c156436be 100644
--- a/arch/x86/include/asm/sgx.h
+++ b/arch/x86/include/asm/sgx.h
@@ -108,6 +108,8 @@ void sgx_free_page(struct sgx_epc_page *page);
 void sgx_page_reclaimable(struct sgx_epc_page *page);
 struct page *sgx_get_backing(struct file *file, pgoff_t index);
 void sgx_put_backing(struct page *backing_page, bool write);
+int sgx_einit(struct sgx_sigstruct *sigstruct, struct sgx_einittoken *token,
+	      struct sgx_epc_page *secs_page, u64 lepubkeyhash[4]);
 
 #define ENCLS_FAULT_FLAG 0x40000000UL
 #define ENCLS_FAULT_FLAG_ASM "$0x40000000"
diff --git a/arch/x86/kernel/cpu/intel_sgx.c b/arch/x86/kernel/cpu/intel_sgx.c
index 1046478a3ab9..fe25e6805680 100644
--- a/arch/x86/kernel/cpu/intel_sgx.c
+++ b/arch/x86/kernel/cpu/intel_sgx.c
@@ -9,6 +9,7 @@
 #include <linux/sched/signal.h>
 #include <linux/shmem_fs.h>
 #include <linux/slab.h>
+#include <linux/suspend.h>
 #include <asm/sgx.h>
 #include <asm/sgx_pr.h>
 
@@ -38,6 +39,18 @@ static LIST_HEAD(sgx_active_page_list);
 static DEFINE_SPINLOCK(sgx_active_page_list_lock);
 static struct task_struct *ksgxswapd_tsk;
 static DECLARE_WAIT_QUEUE_HEAD(ksgxswapd_waitq);
+static struct notifier_block sgx_pm_notifier;
+static u64 sgx_pm_cnt;
+
+/* The cache for the last known values of IA32_SGXLEPUBKEYHASHx MSRs for each
+ * CPU. The entries are initialized when they are first used by sgx_einit().
+ */
+struct sgx_lepubkeyhash {
+	u64 msrs[4];
+	u64 pm_cnt;
+};
+
+static DEFINE_PER_CPU(struct sgx_lepubkeyhash *, sgx_lepubkeyhash_cache);
 
 /**
  * sgx_reclaim_pages - reclaim EPC pages from the consumers
@@ -328,6 +341,54 @@ void sgx_put_backing(struct page *backing_page, bool write)
 }
 EXPORT_SYMBOL_GPL(sgx_put_backing);
 
+/**
+ * sgx_einit - initialize an enclave
+ * @sigstruct:		a pointer to the SIGSTRUCT
+ * @token:		a pointer to the EINITTOKEN
+ * @secs_page:		a pointer to the SECS EPC page
+ * @lepubkeyhash:	the desired value for IA32_SGXLEPUBKEYHASHx MSRs
+ *
+ * Try to perform EINIT operation. If the MSRs are writable, they are updated
+ * according to @lepubkeyhash.
+ *
+ * Return:
+ *   0 on success,
+ *   -errno on failure
+ *   SGX error code if EINIT fails
+ */
+int sgx_einit(struct sgx_sigstruct *sigstruct, struct sgx_einittoken *token,
+	      struct sgx_epc_page *secs_page, u64 lepubkeyhash[4])
+{
+	struct sgx_lepubkeyhash __percpu *cache;
+	bool cache_valid;
+	int i, ret;
+
+	if (!sgx_lc_enabled)
+		return __einit(sigstruct, token, sgx_epc_addr(secs_page));
+
+	cache = per_cpu(sgx_lepubkeyhash_cache, smp_processor_id());
+	if (!cache) {
+		cache = kzalloc(sizeof(struct sgx_lepubkeyhash), GFP_KERNEL);
+		if (!cache)
+			return -ENOMEM;
+	}
+
+	cache_valid = cache->pm_cnt == sgx_pm_cnt;
+	cache->pm_cnt = sgx_pm_cnt;
+	preempt_disable();
+	for (i = 0; i < 4; i++) {
+		if (cache_valid && lepubkeyhash[i] == cache->msrs[i])
+			continue;
+
+		wrmsrl(MSR_IA32_SGXLEPUBKEYHASH0 + i, lepubkeyhash[i]);
+		cache->msrs[i] = lepubkeyhash[i];
+	}
+	ret = __einit(sigstruct, token, sgx_epc_addr(secs_page));
+	preempt_enable();
+	return ret;
+}
+EXPORT_SYMBOL(sgx_einit);
+
 static __init int sgx_init_epc_bank(u64 addr, u64 size, unsigned long index,
 				    struct sgx_epc_bank *bank)
 {
@@ -426,6 +487,15 @@ static __init int sgx_page_cache_init(void)
 	return 0;
 }
 
+static int sgx_pm_notifier_cb(struct notifier_block *nb, unsigned long action,
+			      void *data)
+{
+	if (action == PM_SUSPEND_PREPARE || action == PM_HIBERNATION_PREPARE)
+		sgx_pm_cnt++;
+
+	return NOTIFY_DONE;
+}
+
 static __init int sgx_init(void)
 {
 	struct task_struct *tsk;
@@ -452,20 +522,30 @@ static __init int sgx_init(void)
 	if (!(fc & FEATURE_CONTROL_SGX_LE_WR))
 		pr_info("IA32_SGXLEPUBKEYHASHn MSRs are not writable\n");
 
-	ret = sgx_page_cache_init();
+	sgx_pm_notifier.notifier_call = sgx_pm_notifier_cb;
+	ret = register_pm_notifier(&sgx_pm_notifier);
 	if (ret)
 		return ret;
 
+	ret = sgx_page_cache_init();
+	if (ret)
+		goto out_pm;
+
 	tsk = kthread_run(ksgxswapd, NULL, "ksgxswapd");
 	if (IS_ERR(tsk)) {
-		sgx_page_cache_teardown();
-		return PTR_ERR(tsk);
+		ret = PTR_ERR(tsk);
+		goto out_pcache;
 	}
 	ksgxswapd_tsk = tsk;
 
 	sgx_enabled = true;
 	sgx_lc_enabled = !!(fc & FEATURE_CONTROL_SGX_LE_WR);
 	return 0;
+out_pcache:
+	sgx_page_cache_teardown();
+out_pm:
+	unregister_pm_notifier(&sgx_pm_notifier);
+	return ret;
 }
 
 arch_initcall(sgx_init);
-- 
2.17.1