Re: [PATCHv3 04/17] mm/page_alloc: Handle allocation for encrypted memory

[Dave Hansen]

On 06/12/2018 07:39 AM, Kirill A. Shutemov wrote:
> For encrypted memory, we need to allocated pages for a specific
> encryption KeyID.

"allocate"                         ^

> There are two cases when we need to allocate a page for encryption:
> 
>  - Allocation for an encrypted VMA;
> 
>  - Allocation for migration of encrypted page;
> 
> The first case can be covered within alloc_page_vma().

... because we know the KeyID from the VMA?

> The second case requires few new page allocation routines that would
> allocate the page for a specific KeyID.
> 
> Encrypted page has to be cleared after KeyID set. This is handled by

"An encrypted page has ... "

This description lacks a description of the performance impact of the
approach in this patch both when allocating encrypted and normal pages.

> --- a/arch/alpha/include/asm/page.h
> +++ b/arch/alpha/include/asm/page.h
> @@ -18,7 +18,7 @@ extern void clear_page(void *page);
>  #define clear_user_page(page, vaddr, pg)	clear_page(page)
>  
>  #define __alloc_zeroed_user_highpage(movableflags, vma, vaddr) \
> -	alloc_page_vma(GFP_HIGHUSER | __GFP_ZERO | movableflags, vma, vmaddr)
> +	alloc_page_vma(GFP_HIGHUSER | __GFP_ZERO | movableflags, vma, vaddr)
>  #define __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE

Does this compile?  Wouldn't "vmaddr" be undefined?

> +#define alloc_hugepage_vma(gfp_mask, vma, addr, order) \
> +	alloc_pages_vma(gfp_mask, order, vma, addr, numa_node_id(), true)

The argument addition should be broken out into a preparatory patch.

>  extern unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order);
>  extern unsigned long get_zeroed_page(gfp_t gfp_mask);
> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> index f2b4abbca55e..6da504bad841 100644
> --- a/include/linux/migrate.h
> +++ b/include/linux/migrate.h
> @@ -38,9 +38,11 @@ static inline struct page *new_page_nodemask(struct page *page,
>  	unsigned int order = 0;
>  	struct page *new_page = NULL;
>  
> -	if (PageHuge(page))
> +	if (PageHuge(page)) {
> +		WARN_ON(page_keyid(page));
>  		return alloc_huge_page_nodemask(page_hstate(compound_head(page)),
>  				preferred_nid, nodemask);
> +	}

Comment on the warning, please.

> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 9ac49ef17b4e..00bccbececea 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -920,22 +920,24 @@ static void migrate_page_add(struct page *page, struct list_head *pagelist,
>  /* page allocation callback for NUMA node migration */
>  struct page *alloc_new_node_page(struct page *page, unsigned long node)
>  {
> -	if (PageHuge(page))
> +	if (PageHuge(page)) {
> +		WARN_ON(page_keyid(page));
>  		return alloc_huge_page_node(page_hstate(compound_head(page)),
>  					node);

Comments, please.

> @@ -2012,9 +2014,16 @@ alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
>  {
>  	struct mempolicy *pol;
>  	struct page *page;
> -	int preferred_nid;
> +	bool zero = false;
> +	int keyid, preferred_nid;
>  	nodemask_t *nmask;
>  
> +	keyid = vma_keyid(vma);
> +	if (keyid && gfp & __GFP_ZERO) {
> +		zero = true;
> +		gfp &= ~__GFP_ZERO;
> +	}

I totally read that wrong.

"zero" needs to be named: "page_need_zeroing".

It also badly needs a comment.

>  	pol = get_vma_policy(vma, addr);
>  
>  	if (pol->mode == MPOL_INTERLEAVE) {
> @@ -2057,6 +2066,8 @@ alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
>  	page = __alloc_pages_nodemask(gfp, order, preferred_nid, nmask);
>  	mpol_cond_put(pol);
>  out:
> +	if (page && keyid)
> +		prep_encrypted_page(page, order, keyid, zero);
>  	return page;
>  }

I'd just have prep_encrypted_page() do the keyid-0 opt-out of the prep
work.  It'll be less to patch when you

> diff --git a/mm/migrate.c b/mm/migrate.c
> index 8c0af0f7cab1..eb8dea219dcb 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1847,7 +1847,7 @@ static struct page *alloc_misplaced_dst_page(struct page *page,
>  	int nid = (int) data;
>  	struct page *newpage;
>  
> -	newpage = __alloc_pages_node(nid,
> +	newpage = __alloc_pages_node_keyid(nid, page_keyid(page),
>  					 (GFP_HIGHUSER_MOVABLE |
>  					  __GFP_THISNODE | __GFP_NOMEMALLOC |
>  					  __GFP_NORETRY | __GFP_NOWARN) &

I thought folks asked you not to change all of the calling conventions
across the page allocator.  It seems like you're still doing that,
though.  A reviewer might think you've ignored their earlier feedback.
Did you?


> +#ifndef CONFIG_NUMA
> +struct page *alloc_pages_vma(gfp_t gfp_mask, int order,
> +		struct vm_area_struct *vma, unsigned long addr,
> +		int node, bool hugepage)
> +{
> +	struct page *page;
> +	bool zero = false;
> +	int keyid = vma_keyid(vma);
> +
> +	if (keyid && (gfp_mask & __GFP_ZERO)) {

Please at least do your parenthesis consistently. :)

> +		zero = true;
> +		gfp_mask &= ~__GFP_ZERO;
> +	}
> +
> +	page = alloc_pages(gfp_mask, order);
> +	if (page && keyid)
> +		prep_encrypted_page(page, order, keyid, zero);
> +
> +	return page;
> +}
> +#endif

I'm also confused by the #ifdef.  What is it for?

> +struct page * __alloc_pages_node_keyid(int nid, int keyid,
> +		gfp_t gfp_mask, unsigned int order)
> +{
> +	struct page *page;
> +	bool zero = false;
> +
> +	VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES);
> +	VM_WARN_ON(!node_online(nid));
> +
> +	if (keyid && (gfp_mask & __GFP_ZERO)) {
> +		zero = true;
> +		gfp_mask &= ~__GFP_ZERO;
> +	}

OK, so this is the third time I've seen that pattern.  Are you *sure*
you don't want to consolidate the sites?

> +	page = __alloc_pages(gfp_mask, order, nid);
> +	if (page && keyid)
> +		prep_encrypted_page(page, order, keyid, zero);
> +
> +	return page;
> +}
> +
>  #ifdef CONFIG_LOCKDEP
>  struct lockdep_map __fs_reclaim_map =
>  	STATIC_LOCKDEP_MAP_INIT("fs_reclaim", &__fs_reclaim_map);
> @@ -4396,6 +4439,26 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, int preferred_nid,
>  }
>  EXPORT_SYMBOL(__alloc_pages_nodemask);
>  
> +struct page *
> +__alloc_pages_nodemask_keyid(gfp_t gfp_mask, unsigned int order,
> +		int preferred_nid, nodemask_t *nodemask, int keyid)
> +{
> +	struct page *page;
> +	bool zero = false;
> +
> +	if (keyid && (gfp_mask & __GFP_ZERO)) {
> +		zero = true;
> +		gfp_mask &= ~__GFP_ZERO;
> +	}

Fourth one. :)