Re: [PATCH] s390/mm: Make virt_to_pfn() a static inline

[Alexander Gordeev]

On Fri, Aug 11, 2023 at 09:02:47AM +0200, Linus Walleij wrote:
> Making virt_to_pfn() a static inline taking a strongly typed
> (const void *) makes the contract of a passing a pointer of that
> type to the function explicit and exposes any misuse of the
> macro virt_to_pfn() acting polymorphic and accepting many types
> such as (void *), (unitptr_t) or (unsigned long) as arguments
> without warnings.
> 
> For symmetry do the same with pfn_to_virt() reflecting the
> current layout in asm-generic/page.h.
> 
> Doing this reveals a number of offenders in the arch code and
> the S390-specific drivers, so just bite the bullet and fix up
> all of those as well.

Funnily enough, except drivers/s390/char/vmcp.c none of affected
code pieces below is an offender. But anyway, to me it looks like
a nice improvement.

> Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
> ---
>  arch/s390/include/asm/kfence.h |  2 +-
>  arch/s390/include/asm/page.h   | 12 ++++++++++--
>  arch/s390/mm/cmm.c             |  2 +-
>  arch/s390/mm/vmem.c            |  2 +-
>  drivers/s390/block/scm_blk.c   |  2 +-
>  drivers/s390/char/vmcp.c       |  2 +-
>  6 files changed, 15 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/s390/include/asm/kfence.h b/arch/s390/include/asm/kfence.h
> index d55ba878378b..e47fd8cbe701 100644
> --- a/arch/s390/include/asm/kfence.h
> +++ b/arch/s390/include/asm/kfence.h
> @@ -35,7 +35,7 @@ static __always_inline void kfence_split_mapping(void)
>  
>  static inline bool kfence_protect_page(unsigned long addr, bool protect)
>  {
> -	__kernel_map_pages(virt_to_page(addr), 1, !protect);
> +	__kernel_map_pages(virt_to_page((void *)addr), 1, !protect);
>  	return true;
>  }
>  
> diff --git a/arch/s390/include/asm/page.h b/arch/s390/include/asm/page.h
> index a9c138fcd2ad..cfec0743314e 100644
> --- a/arch/s390/include/asm/page.h
> +++ b/arch/s390/include/asm/page.h
> @@ -191,8 +191,16 @@ int arch_make_page_accessible(struct page *page);
>  #define phys_to_page(phys)	pfn_to_page(phys_to_pfn(phys))
>  #define page_to_phys(page)	pfn_to_phys(page_to_pfn(page))
>  
> -#define pfn_to_virt(pfn)	__va(pfn_to_phys(pfn))
> -#define virt_to_pfn(kaddr)	(phys_to_pfn(__pa(kaddr)))
> +static inline void *pfn_to_virt(unsigned long pfn)
> +{
> +	return __va(pfn_to_phys(pfn));
> +}
> +
> +static inline unsigned long virt_to_pfn(const void *kaddr)
> +{
> +	return phys_to_pfn(__pa(kaddr));
> +}
> +
>  #define pfn_to_kaddr(pfn)	pfn_to_virt(pfn)
>  
>  #define virt_to_page(kaddr)	pfn_to_page(virt_to_pfn(kaddr))
> diff --git a/arch/s390/mm/cmm.c b/arch/s390/mm/cmm.c
> index 5300c6867d5e..f47515313226 100644
> --- a/arch/s390/mm/cmm.c
> +++ b/arch/s390/mm/cmm.c
> @@ -90,7 +90,7 @@ static long cmm_alloc_pages(long nr, long *counter,
>  			} else
>  				free_page((unsigned long) npa);
>  		}
> -		diag10_range(virt_to_pfn(addr), 1);
> +		diag10_range(virt_to_pfn((void *)addr), 1);
>  		pa->pages[pa->index++] = addr;
>  		(*counter)++;
>  		spin_unlock(&cmm_lock);
> diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c
> index b26649233d12..30cd6e1be10d 100644
> --- a/arch/s390/mm/vmem.c
> +++ b/arch/s390/mm/vmem.c
> @@ -36,7 +36,7 @@ static void vmem_free_pages(unsigned long addr, int order)
>  {
>  	/* We don't expect boot memory to be removed ever. */
>  	if (!slab_is_available() ||
> -	    WARN_ON_ONCE(PageReserved(virt_to_page(addr))))
> +	    WARN_ON_ONCE(PageReserved(virt_to_page((void *)addr))))
>  		return;
>  	free_pages(addr, order);
>  }
> diff --git a/drivers/s390/block/scm_blk.c b/drivers/s390/block/scm_blk.c
> index 0c1df1d5f1ac..3a9cc8a4a230 100644
> --- a/drivers/s390/block/scm_blk.c
> +++ b/drivers/s390/block/scm_blk.c
> @@ -134,7 +134,7 @@ static void scm_request_done(struct scm_request *scmrq)
>  
>  		if ((msb->flags & MSB_FLAG_IDA) && aidaw &&
>  		    IS_ALIGNED(aidaw, PAGE_SIZE))
> -			mempool_free(virt_to_page(aidaw), aidaw_pool);
> +			mempool_free(virt_to_page((void *)aidaw), aidaw_pool);
>  	}
>  
>  	spin_lock_irqsave(&list_lock, flags);
> diff --git a/drivers/s390/char/vmcp.c b/drivers/s390/char/vmcp.c
> index 4cebfaaa22b4..f66906da83c4 100644
> --- a/drivers/s390/char/vmcp.c
> +++ b/drivers/s390/char/vmcp.c
> @@ -89,7 +89,7 @@ static void vmcp_response_free(struct vmcp_session *session)
>  	order = get_order(session->bufsize);
>  	nr_pages = ALIGN(session->bufsize, PAGE_SIZE) >> PAGE_SHIFT;
>  	if (session->cma_alloc) {
> -		page = virt_to_page((unsigned long)session->response);
> +		page = virt_to_page((void *)session->response);

The cast to (void *) is extra, if I read your commit message
correctly: "...makes the contract of a passing a pointer of that
type to the function explicit..."

>  		cma_release(vmcp_cma, page, nr_pages);
>  		session->cma_alloc = 0;
>  	} else {
> 
> ---
> base-commit: 06c2afb862f9da8dc5efa4b6076a0e48c3fbaaa5
> change-id: 20230809-virt-to-phys-s390-2fa3d38b8855

Thanks, Linus!

> Best regards,
> -- 
> Linus Walleij <linus.walleij@xxxxxxxxxx>
>