Re: [PATCH 3/4] s390/mm: Add __context_unsafe() attribute to gmap helper functions

[Claudio Imbrenda]

On Mon,  3 Aug 2026 19:21:43 +0200
Heiko Carstens <hca@xxxxxxxxxxxxx> wrote:

> Disable context analysis for various gmap helper functions to get rid
> of a few warnings:
> 
> arch/s390/mm/gmap_helpers.c:80:1: warning: spinlock 'ptl' is not held on every path through here
> arch/s390/mm/gmap_helpers.c:116:2: warning: releasing spinlock 'ptl' that was not held
> arch/s390/mm/gmap_helpers.c:186:2: warning: releasing spinlock 'ptl' that was not held
> 
> Use __context_unsafe() to give a short comment why for function context
> analysis is disabled.
> 
> try_get_locked_pte() is disabled since it may return a nonull value
> regardless if it returns with a lock held or not.
> 
> This cannot be reflected with the context analysis attributes. It is
> however possible to workaround this e.g. by adding a another `contended`
> function parameter, however this would lead to the next problem:
> pte_unmap_unlock() is a macro and therefore doesn't come with the
> required context analysis attribute to address this.
> 
> For that reason also disable context analysis for
> gmap_helper_zap_one_page() and gmap_helper_try_set_pte_unused()
> until this has been addressed.
> 
> Signed-off-by: Heiko Carstens <hca@xxxxxxxxxxxxx>

Acked-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>

> ---
>  arch/s390/mm/gmap_helpers.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/s390/mm/gmap_helpers.c b/arch/s390/mm/gmap_helpers.c
> index 4bf7c9012feb..f910c9584560 100644
> --- a/arch/s390/mm/gmap_helpers.c
> +++ b/arch/s390/mm/gmap_helpers.c
> @@ -40,6 +40,7 @@
>   *   and locked.
>   */
>  pte_t *try_get_locked_pte(struct mm_struct *mm, unsigned long vmaddr, spinlock_t **ptl)
> +__context_unsafe(/* Returns nonnull if lock taken or not taken */)
>  {
>  	pmd_t *pmdp, pmd, pmdval;
>  	pud_t *pudp, pud;
> @@ -90,6 +91,7 @@ EXPORT_SYMBOL_GPL(try_get_locked_pte);
>   * Context: needs to be called while holding the mmap lock.
>   */
>  void gmap_helper_zap_one_page(struct mm_struct *mm, unsigned long vmaddr)
> +__context_unsafe(/* pte_unmap_unlock() not instrumented */)
>  {
>  	struct vm_area_struct *vma;
>  	spinlock_t *ptl;	/* Lock for the host (userspace) page table */
> @@ -161,6 +163,7 @@ EXPORT_SYMBOL_GPL(gmap_helper_discard);
>   *          disabled.
>   */
>  void gmap_helper_try_set_pte_unused(struct mm_struct *mm, unsigned long vmaddr)
> +__context_unsafe(/* pte_unmap_unlock() not instrumented */)
>  {
>  	spinlock_t *ptl;	/* Lock for the host (userspace) page table */
>  	pte_t *ptep;