[PATCH 2/3] x86/sgx: Only run the reclaimer when the native SGX driver is enabled

[Kai Huang]

Currently the EPC pages assigned to KVM guests cannot be reclaimed, so
there's no point to run the reclaimer when the native SGX driver is not
enabled.

Add a function to indicate whether the native SGX driver has been
initialized, and in ksgxd(), avoid running the reclaimer when it is
false.

In sgx_drv_init(), move the register of "/dev/sgx_enclave" misc device
before initializing sgx_attributes_reserved_mask (and the other two
masks) so that the new function can just use it to determine whether the
SGX driver has been initialized w/o introducing a new boolean.

Signed-off-by: Kai Huang <kai.huang@xxxxxxxxx>
---
 arch/x86/kernel/cpu/sgx/driver.c | 13 +++++++++----
 arch/x86/kernel/cpu/sgx/driver.h |  1 +
 arch/x86/kernel/cpu/sgx/main.c   | 11 ++++++++++-
 3 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/driver.c b/arch/x86/kernel/cpu/sgx/driver.c
index aa9b8b868867..b5e754632eed 100644
--- a/arch/x86/kernel/cpu/sgx/driver.c
+++ b/arch/x86/kernel/cpu/sgx/driver.c
@@ -160,6 +160,10 @@ int __init sgx_drv_init(void)
 		return -ENODEV;
 	}
 
+	ret = misc_register(&sgx_dev_enclave);
+	if (ret)
+		return ret;
+
 	sgx_misc_reserved_mask = ~ebx | SGX_MISC_RESERVED_MASK;
 
 	cpuid_count(SGX_CPUID, 1, &eax, &ebx, &ecx, &edx);
@@ -172,9 +176,10 @@ int __init sgx_drv_init(void)
 		sgx_xfrm_reserved_mask = ~xfrm_mask;
 	}
 
-	ret = misc_register(&sgx_dev_enclave);
-	if (ret)
-		return ret;
-
 	return 0;
 }
+
+bool sgx_drv_inited(void)
+{
+	return !!sgx_attributes_reserved_mask;
+}
diff --git a/arch/x86/kernel/cpu/sgx/driver.h b/arch/x86/kernel/cpu/sgx/driver.h
index 4eddb4d571ef..159cc066e9cb 100644
--- a/arch/x86/kernel/cpu/sgx/driver.h
+++ b/arch/x86/kernel/cpu/sgx/driver.h
@@ -25,5 +25,6 @@ extern const struct file_operations sgx_provision_fops;
 long sgx_ioctl(struct file *filep, unsigned int cmd, unsigned long arg);
 
 int sgx_drv_init(void);
+bool sgx_drv_inited(void);
 
 #endif /* __ARCH_X86_SGX_DRIVER_H__ */
diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index 713ca09f6d6e..0fdbc490b0f8 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -403,6 +403,14 @@ static int ksgxd(void *p)
 	__sgx_sanitize_pages(&sgx_dirty_page_list);
 	WARN_ON(__sgx_sanitize_pages(&sgx_dirty_page_list));
 
+	/*
+	 * EPC pages assigned to KVM guests cannot be reclaimed.  There's
+	 * no reason to run the reclaimer if the native SGX driver isn't
+	 * initialized successfully (i.e. on the machines w/o SGX_LC).
+	 */
+	if (!sgx_drv_inited())
+		return 0;
+
 	while (!kthread_should_stop()) {
 		if (try_to_freeze())
 			continue;
@@ -940,7 +948,8 @@ static int __init sgx_init(void)
 		ksgxd_tsk = NULL;
 		__sgx_sanitize_pages(&sgx_dirty_page_list);
 		WARN_ON(__sgx_sanitize_pages(&sgx_dirty_page_list));
-		pr_info("Running SGX w/o EPC page reclaimer.\n");
+		if (sgx_drv_inited())
+			pr_info("Running native SGX driver w/o EPC page reclaimer.\n");
 	}
 
 	return 0;
-- 
2.37.1