On Mon, 2025-05-19 at 10:24 +0300, Elena Reshetova wrote:
> 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();
This should be done at the end of sgx_open() where the open cannot fail, since
sgx_release() is not called if sgx_open() failed AFAICT.
> 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;
> +}
What's the purpose of the returning int? Seems no caller uses the return value.
> +
> +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();
Ditto to sgx_open().
> vepc = kzalloc(sizeof(struct sgx_vepc), GFP_KERNEL);
> if (!vepc)
> return -ENOMEM;
