linux-kernel - Re: [PATCH v2 09/10] s390/uv: implement HAVE_ARCH_MAKE_FOLIO

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Date: Tue, 7 May 2024 18:29:30 +0200
From: Claudio Imbrenda <imbrenda@...ux.ibm.com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-s390@...r.kernel.org, Heiko Carstens <hca@...ux.ibm.com>,
        Vasily
 Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle
 <svens@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Gerald
 Schaefer <gerald.schaefer@...ux.ibm.com>,
        Matthew Wilcox
 <willy@...radead.org>, Thomas Huth <thuth@...hat.com>
Subject: Re: [PATCH v2 09/10] s390/uv: implement
 HAVE_ARCH_MAKE_FOLIO_ACCESSIBLE

On Fri, 12 Apr 2024 16:21:19 +0200
David Hildenbrand <david@...hat.com> wrote:

> Let's also implement HAVE_ARCH_MAKE_FOLIO_ACCESSIBLE, so we can convert
> arch_make_page_accessible() to be a simple wrapper around
> arch_make_folio_accessible(). Unfortuantely, we cannot do that in the
> header.
> 
> There are only two arch_make_page_accessible() calls remaining in gup.c.
> We can now drop HAVE_ARCH_MAKE_PAGE_ACCESSIBLE completely form core-MM.
> We'll handle that separately, once the s390x part landed.
> 
> Suggested-by: Matthew Wilcox <willy@...radead.org>
> Signed-off-by: David Hildenbrand <david@...hat.com>

Reviewed-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>

> ---
>  arch/s390/include/asm/page.h |  3 +++
>  arch/s390/kernel/uv.c        | 18 +++++++++++-------
>  arch/s390/mm/fault.c         | 14 ++++++++------
>  3 files changed, 22 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/s390/include/asm/page.h b/arch/s390/include/asm/page.h
> index b64384872c0f..03bbc782e286 100644
> --- a/arch/s390/include/asm/page.h
> +++ b/arch/s390/include/asm/page.h
> @@ -162,6 +162,7 @@ static inline int page_reset_referenced(unsigned long addr)
>  #define _PAGE_ACC_BITS		0xf0	/* HW access control bits	*/
>  
>  struct page;
> +struct folio;
>  void arch_free_page(struct page *page, int order);
>  void arch_alloc_page(struct page *page, int order);
>  
> @@ -174,6 +175,8 @@ static inline int devmem_is_allowed(unsigned long pfn)
>  #define HAVE_ARCH_ALLOC_PAGE
>  
>  #if IS_ENABLED(CONFIG_PGSTE)
> +int arch_make_folio_accessible(struct folio *folio);
> +#define HAVE_ARCH_MAKE_FOLIO_ACCESSIBLE
>  int arch_make_page_accessible(struct page *page);
>  #define HAVE_ARCH_MAKE_PAGE_ACCESSIBLE
>  #endif
> diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
> index b456066d72da..fa62fa0e369f 100644
> --- a/arch/s390/kernel/uv.c
> +++ b/arch/s390/kernel/uv.c
> @@ -498,14 +498,13 @@ int gmap_destroy_page(struct gmap *gmap, unsigned long gaddr)
>  EXPORT_SYMBOL_GPL(gmap_destroy_page);
>  
>  /*
> - * To be called with the page locked or with an extra reference! This will
> - * prevent gmap_make_secure from touching the page concurrently. Having 2
> - * parallel make_page_accessible is fine, as the UV calls will become a
> - * no-op if the page is already exported.
> + * To be called with the folio locked or with an extra reference! This will
> + * prevent gmap_make_secure from touching the folio concurrently. Having 2
> + * parallel arch_make_folio_accessible is fine, as the UV calls will become a
> + * no-op if the folio is already exported.
>   */
> -int arch_make_page_accessible(struct page *page)
> +int arch_make_folio_accessible(struct folio *folio)
>  {
> -	struct folio *folio = page_folio(page);
>  	int rc = 0;
>  
>  	/* See gmap_make_secure(): large folios cannot be secure */
> @@ -537,8 +536,13 @@ int arch_make_page_accessible(struct page *page)
>  
>  	return rc;
>  }
> -EXPORT_SYMBOL_GPL(arch_make_page_accessible);
> +EXPORT_SYMBOL_GPL(arch_make_folio_accessible);
>  
> +int arch_make_page_accessible(struct page *page)
> +{
> +	return arch_make_folio_accessible(page_folio(page));
> +}
> +EXPORT_SYMBOL_GPL(arch_make_page_accessible);
>  #endif
>  
>  #if defined(CONFIG_PROTECTED_VIRTUALIZATION_GUEST) || IS_ENABLED(CONFIG_KVM)
> diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
> index c421dd44ffbe..a1ba58460593 100644
> --- a/arch/s390/mm/fault.c
> +++ b/arch/s390/mm/fault.c
> @@ -491,6 +491,7 @@ void do_secure_storage_access(struct pt_regs *regs)
>  	unsigned long addr = get_fault_address(regs);
>  	struct vm_area_struct *vma;
>  	struct mm_struct *mm;
> +	struct folio *folio;
>  	struct page *page;
>  	struct gmap *gmap;
>  	int rc;
> @@ -538,17 +539,18 @@ void do_secure_storage_access(struct pt_regs *regs)
>  			mmap_read_unlock(mm);
>  			break;
>  		}
> -		if (arch_make_page_accessible(page))
> +		folio = page_folio(page);
> +		if (arch_make_folio_accessible(folio))
>  			send_sig(SIGSEGV, current, 0);
> -		put_page(page);
> +		folio_put(folio);
>  		mmap_read_unlock(mm);
>  		break;
>  	case KERNEL_FAULT:
> -		page = phys_to_page(addr);
> -		if (unlikely(!try_get_page(page)))
> +		folio = phys_to_folio(addr);
> +		if (unlikely(!folio_try_get(folio)))
>  			break;
> -		rc = arch_make_page_accessible(page);
> -		put_page(page);
> +		rc = arch_make_folio_accessible(folio);
> +		folio_put(folio);
>  		if (rc)
>  			BUG();
>  		break;