Re: [PATCH v4 1/2] mm: Add a vmf_insert_mixed_prot() function

[Thomas Hellstrom]

On 12/12/19 9:48 AM, Thomas Hellström (VMware) wrote:
> From: Thomas Hellstrom <thellstrom@xxxxxxxxxx>
>
> The TTM module today uses a hack to be able to set a different page
> protection than struct vm_area_struct::vm_page_prot. To be able to do
> this properly, add the needed vm functionality as vmf_insert_mixed_prot().
>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
> Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
> Cc: Ralph Campbell <rcampbell@xxxxxxxxxx>
> Cc: "Jérôme Glisse" <jglisse@xxxxxxxxxx>
> Cc: "Christian König" <christian.koenig@xxxxxxx>
> Signed-off-by: Thomas Hellstrom <thellstrom@xxxxxxxxxx>
> Acked-by: Christian König <christian.koenig@xxxxxxx>
> ---
>  include/linux/mm.h       |  2 ++
>  include/linux/mm_types.h |  7 ++++++-
>  mm/memory.c              | 43 ++++++++++++++++++++++++++++++++++++----
>  3 files changed, 47 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index cc292273e6ba..29575d3c1e47 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2548,6 +2548,8 @@ vm_fault_t vmf_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
>  			unsigned long pfn, pgprot_t pgprot);
>  vm_fault_t vmf_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
>  			pfn_t pfn);
> +vm_fault_t vmf_insert_mixed_prot(struct vm_area_struct *vma, unsigned long addr,
> +			pfn_t pfn, pgprot_t pgprot);
>  vm_fault_t vmf_insert_mixed_mkwrite(struct vm_area_struct *vma,
>  		unsigned long addr, pfn_t pfn);
>  int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len);
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 2222fa795284..ac96afdbb4bc 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -307,7 +307,12 @@ struct vm_area_struct {
>  	/* Second cache line starts here. */
>  
>  	struct mm_struct *vm_mm;	/* The address space we belong to. */
> -	pgprot_t vm_page_prot;		/* Access permissions of this VMA. */
> +
> +	/*
> +	 * Access permissions of this VMA.
> +	 * See vmf_insert_mixed() for discussion.

Typo. will of course be vmf_insert_mixed_prot() in the final version.