Re: [PATCH v2] x86/sgx: Migrate to mmu_notifier_put()

[Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>]

On Thu, Oct 03, 2019 at 08:04:23PM +0300, Jarkko Sakkinen wrote:
> Use mmu_notifier_put() to synchronize sgx_encl_mm deletion.
> 
> Cc: Sean Christopherson <sean.j.christopherson@intel.com>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> ---
> v2:
> * Was not thinking clearly that we also use it for lockless
>   operation on the mm list. Just migrating to mmu_notifier_put().
>   Please ignore the previous patch!
>  arch/x86/kernel/cpu/sgx/encl.c | 26 ++++++++++----------------
>  1 file changed, 10 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
> index d145360380d5..8cc9ea353bee 100644
> --- a/arch/x86/kernel/cpu/sgx/encl.c
> +++ b/arch/x86/kernel/cpu/sgx/encl.c
> @@ -131,14 +131,6 @@ static struct sgx_encl_page *sgx_encl_load_page(struct sgx_encl *encl,
>  	return entry;
>  }
>  
> -static void sgx_encl_mm_release_deferred(struct rcu_head *rcu)
> -{
> -	struct sgx_encl_mm *encl_mm =
> -		container_of(rcu, struct sgx_encl_mm, rcu);
> -
> -	kfree(encl_mm);
> -}
> -
>  static void sgx_mmu_notifier_release(struct mmu_notifier *mn,
>  				     struct mm_struct *mm)
>  {
> @@ -161,19 +153,21 @@ static void sgx_mmu_notifier_release(struct mmu_notifier *mn,
>  
>  	if (tmp == encl_mm) {
>  		synchronize_srcu(&encl_mm->encl->srcu);
> -
> -		/*
> -		 * Delay freeing encl_mm until after mmu_notifier synchronizes
> -		 * its SRCU to ensure encl_mm cannot be dereferenced.
> -		 */
> -		mmu_notifier_unregister_no_release(mn, mm);
> -		mmu_notifier_call_srcu(&encl_mm->rcu,
> -				       &sgx_encl_mm_release_deferred);
> +		mmu_notifier_put(mn);
>  	}
>  }
>  
> +static void sgx_mmu_notifier_free(struct mmu_notifier *mn)
> +{
> +	struct sgx_encl_mm *encl_mm =
> +		container_of(mn, struct sgx_encl_mm, mmu_notifier);
> +
> +	kfree(encl_mm);
> +}
> +
>  static const struct mmu_notifier_ops sgx_mmu_notifier_ops = {
>  	.release		= sgx_mmu_notifier_release,
> +	.free_notifier		= sgx_mmu_notifier_free,
>  };
>  
>  static struct sgx_encl_mm *sgx_encl_find_mm(struct sgx_encl *encl,
> -- 
> 2.20.1
> 

This one I squashed (master updated).

/Jarkko