Re: [PATCH v9 6/6] x86/sgx: Enable automatic SVN updates for SGX enclaves

["Huang, Kai" <kai.huang@intel.com>]

>  /* Counter to count the active SGX users */
>  static int __maybe_unused sgx_usage_count;

Seems you forgot to remove this __maybe_unused.

I think you can just introduce 'sgx_usage_count' in this patch.

>  
> +/* Mutex to ensure no concurrent EPC accesses during EUPDATESVN */
> +static DEFINE_MUTEX(sgx_svn_lock);
> +
>  /**
>   * sgx_update_svn() - Attempt to call ENCLS[EUPDATESVN].
>   * This instruction attempts to update CPUSVN to the
> @@ -937,7 +940,7 @@ static int __maybe_unused sgx_usage_count;
>   *  entropy in RNG.
>   * -EIO: Unexpected error, retries are not advisable.
>   */
> -static int __maybe_unused sgx_update_svn(void)
> +static int sgx_update_svn(void)
>  {
>  	int ret;
>  
> @@ -983,12 +986,17 @@ static int __maybe_unused sgx_update_svn(void)
>  
>  int sgx_inc_usage_count(void)
>  {
> +	guard(mutex)(&sgx_svn_lock);
> +
> +	if (sgx_usage_count++ == 0)
> +		return sgx_update_svn();
> +
>  	return 0;
>  }
>  
>  void sgx_dec_usage_count(void)
>  {
> -	return;
> +	sgx_usage_count--;
>  }
>  
>  static int __init sgx_init(void)
> -- 
> 2.45.2