[PATCH v5 1/5] x86/sgx: Introduce a counter to count the sgx_(vepc_)open()

[Elena Reshetova]

Currently SGX does not have a global counter to count the
active users from userspace or hypervisor. Implement such a counter,
sgx_usage_count. It will be used by the driver when attempting
to call EUPDATESVN SGX instruction.

Suggested-by: Sean Christopherson <sea...@google.com>
Signed-off-by: Elena Reshetova <elena.reshet...@intel.com>
---
 arch/x86/kernel/cpu/sgx/driver.c |  1 +
 arch/x86/kernel/cpu/sgx/encl.c   |  1 +
 arch/x86/kernel/cpu/sgx/main.c   | 14 ++++++++++++++
 arch/x86/kernel/cpu/sgx/sgx.h    |  3 +++
 arch/x86/kernel/cpu/sgx/virt.c   |  2 ++
 5 files changed, 21 insertions(+)

diff --git a/arch/x86/kernel/cpu/sgx/driver.c b/arch/x86/kernel/cpu/sgx/driver.c
index 7f8d1e11dbee..b5ffe104af4c 100644
--- a/arch/x86/kernel/cpu/sgx/driver.c
+++ b/arch/x86/kernel/cpu/sgx/driver.c
@@ -19,6 +19,7 @@ static int sgx_open(struct inode *inode, struct file *file)
        struct sgx_encl *encl;
        int ret;
 
+       sgx_inc_usage_count();
        encl = kzalloc(sizeof(*encl), GFP_KERNEL);
        if (!encl)
                return -ENOMEM;
diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
index 279148e72459..3b54889ae4a4 100644
--- a/arch/x86/kernel/cpu/sgx/encl.c
+++ b/arch/x86/kernel/cpu/sgx/encl.c
@@ -765,6 +765,7 @@ void sgx_encl_release(struct kref *ref)
        WARN_ON_ONCE(encl->secs.epc_page);
 
        kfree(encl);
+       sgx_dec_usage_count();
 }
 
 /*
diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
index 8ce352fc72ac..80d565e6f2ad 100644
--- a/arch/x86/kernel/cpu/sgx/main.c
+++ b/arch/x86/kernel/cpu/sgx/main.c
@@ -914,6 +914,20 @@ int sgx_set_attribute(unsigned long *allowed_attributes,
 }
 EXPORT_SYMBOL_GPL(sgx_set_attribute);
 
+/* Counter to count the active SGX users */
+static atomic64_t sgx_usage_count;
+
+int sgx_inc_usage_count(void)
+{
+       atomic64_inc(&sgx_usage_count);
+       return 0;
+}
+
+void sgx_dec_usage_count(void)
+{
+       atomic64_dec(&sgx_usage_count);
+}
+
 static int __init sgx_init(void)
 {
        int ret;
diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h
index d2dad21259a8..f5940393d9bd 100644
--- a/arch/x86/kernel/cpu/sgx/sgx.h
+++ b/arch/x86/kernel/cpu/sgx/sgx.h
@@ -102,6 +102,9 @@ static inline int __init sgx_vepc_init(void)
 }
 #endif
 
+int sgx_inc_usage_count(void);
+void sgx_dec_usage_count(void);
+
 void sgx_update_lepubkeyhash(u64 *lepubkeyhash);
 
 #endif /* _X86_SGX_H */
diff --git a/arch/x86/kernel/cpu/sgx/virt.c b/arch/x86/kernel/cpu/sgx/virt.c
index 7aaa3652e31d..83de0907f32c 100644
--- a/arch/x86/kernel/cpu/sgx/virt.c
+++ b/arch/x86/kernel/cpu/sgx/virt.c
@@ -255,6 +255,7 @@ static int sgx_vepc_release(struct inode *inode, struct 
file *file)
        xa_destroy(&vepc->page_array);
        kfree(vepc);
 
+       sgx_dec_usage_count();
        return 0;
 }
 
@@ -262,6 +263,7 @@ static int sgx_vepc_open(struct inode *inode, struct file 
*file)
 {
        struct sgx_vepc *vepc;
 
+       sgx_inc_usage_count();
        vepc = kzalloc(sizeof(struct sgx_vepc), GFP_KERNEL);
        if (!vepc)
                return -ENOMEM;
-- 
2.45.2