Re: [PATCH, RFC 05/62] mm/page_alloc: Handle allocation for encrypted memory

From: Mike Rapoport
Date: Wed May 29 2019 - 03:25:05 EST

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On Wed, May 08, 2019 at 05:43:25PM +0300, Kirill A. Shutemov wrote:
> For encrypted memory, we need to allocate pages for a specific
> encryption KeyID.
>
> 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(). We know KeyID
> from the VMA.
>
> The second case requires few new page allocation routines that would
> allocate the page for a specific KeyID.
>
> An encrypted page has to be cleared after KeyID set. This is handled
> in prep_encrypted_page() that will be provided by arch-specific code.
>
> Any custom allocator that dials with encrypted pages has to call

Nit: ^ deals

> prep_encrypted_page() too. See compaction_alloc() for instance.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> ---
> include/linux/gfp.h | 45 ++++++++++++++++++++++++++++++++-----
> include/linux/migrate.h | 14 +++++++++---
> mm/compaction.c | 3 +++
> mm/mempolicy.c | 27 ++++++++++++++++------
> mm/migrate.c | 4 ++--
> mm/page_alloc.c | 50 +++++++++++++++++++++++++++++++++++++++++
> 6 files changed, 126 insertions(+), 17 deletions(-)
>
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index b101aa294157..1716dbe587c9 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -463,16 +463,43 @@ static inline void arch_free_page(struct page *page, int order) { }
> static inline void arch_alloc_page(struct page *page, int order) { }
> #endif
>
> +#ifndef prep_encrypted_page

An explanation of what is expected from the architecture specific
implementation would be nice.

> +static inline void prep_encrypted_page(struct page *page, int order,
> + int keyid, bool zero)
> +{
> +}
> +#endif
> +
> +/*
> + * Encrypted page has to be cleared once keyid is set, not on allocation.
> + */
> +static inline bool deferred_page_zero(int keyid, gfp_t *gfp_mask)
> +{
> + if (keyid && (*gfp_mask & __GFP_ZERO)) {
> + *gfp_mask &= ~__GFP_ZERO;
> + return true;
> + }
> +
> + return false;
> +}
> +
> struct page *
> __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, int preferred_nid,
> nodemask_t *nodemask);
>
> +struct page *
> +__alloc_pages_nodemask_keyid(gfp_t gfp_mask, unsigned int order,
> + int preferred_nid, nodemask_t *nodemask, int keyid);
> +
> static inline struct page *
> __alloc_pages(gfp_t gfp_mask, unsigned int order, int preferred_nid)
> {
> return __alloc_pages_nodemask(gfp_mask, order, preferred_nid, NULL);
> }
>
> +struct page *__alloc_pages_node_keyid(int nid, int keyid,
> + gfp_t gfp_mask, unsigned int order);
> +
> /*
> * Allocate pages, preferring the node given as nid. The node must be valid and
> * online. For more general interface, see alloc_pages_node().
> @@ -500,6 +527,19 @@ static inline struct page *alloc_pages_node(int nid, gfp_t gfp_mask,
> return __alloc_pages_node(nid, gfp_mask, order);
> }
>
> +static inline struct page *alloc_pages_node_keyid(int nid, int keyid,
> + gfp_t gfp_mask, unsigned int order)
> +{
> + if (nid == NUMA_NO_NODE)
> + nid = numa_mem_id();
> +
> + return __alloc_pages_node_keyid(nid, keyid, gfp_mask, order);
> +}
> +
> +extern struct page *alloc_pages_vma(gfp_t gfp_mask, int order,
> + struct vm_area_struct *vma, unsigned long addr,
> + int node, bool hugepage);
> +
> #ifdef CONFIG_NUMA
> extern struct page *alloc_pages_current(gfp_t gfp_mask, unsigned order);
>
> @@ -508,14 +548,9 @@ alloc_pages(gfp_t gfp_mask, unsigned int order)
> {
> return alloc_pages_current(gfp_mask, order);
> }
> -extern struct page *alloc_pages_vma(gfp_t gfp_mask, int order,
> - struct vm_area_struct *vma, unsigned long addr,
> - int node, bool hugepage);
> #else
> #define alloc_pages(gfp_mask, order) \
> alloc_pages_node(numa_node_id(), gfp_mask, order)
> -#define alloc_pages_vma(gfp_mask, order, vma, addr, node, false)\
> - alloc_pages(gfp_mask, order)
> #endif
> #define alloc_page(gfp_mask) alloc_pages(gfp_mask, 0)
> #define alloc_page_vma(gfp_mask, vma, addr) \
> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> index e13d9bf2f9a5..a6e068762d08 100644
> --- a/include/linux/migrate.h
> +++ b/include/linux/migrate.h
> @@ -38,9 +38,16 @@ 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)) {
> + /*
> + * HugeTLB doesn't support encryption. We shouldn't see
> + * such pages.
> + */
> + if (WARN_ON_ONCE(page_keyid(page)))
> + return NULL;
> return alloc_huge_page_nodemask(page_hstate(compound_head(page)),
> preferred_nid, nodemask);
> + }
>
> if (PageTransHuge(page)) {
> gfp_mask |= GFP_TRANSHUGE;
> @@ -50,8 +57,9 @@ static inline struct page *new_page_nodemask(struct page *page,
> if (PageHighMem(page) || (zone_idx(page_zone(page)) == ZONE_MOVABLE))
> gfp_mask |= __GFP_HIGHMEM;
>
> - new_page = __alloc_pages_nodemask(gfp_mask, order,
> - preferred_nid, nodemask);
> + /* Allocate a page with the same KeyID as the source page */
> + new_page = __alloc_pages_nodemask_keyid(gfp_mask, order,
> + preferred_nid, nodemask, page_keyid(page));
>
> if (new_page && PageTransHuge(new_page))
> prep_transhuge_page(new_page);
> diff --git a/mm/compaction.c b/mm/compaction.c
> index 3319e0872d01..559b8bd6d245 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -1557,6 +1557,9 @@ static struct page *compaction_alloc(struct page *migratepage,
> list_del(&freepage->lru);
> cc->nr_freepages--;
>
> + /* Prepare the page using the same KeyID as the source page */
> + if (freepage)
> + prep_encrypted_page(freepage, 0, page_keyid(migratepage), false);
> return freepage;
> }
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 14b18449c623..5cad39fb7b35 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -961,22 +961,29 @@ 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)) {
> + /*
> + * HugeTLB doesn't support encryption. We shouldn't see
> + * such pages.
> + */
> + if (WARN_ON_ONCE(page_keyid(page)))
> + return NULL;
> return alloc_huge_page_node(page_hstate(compound_head(page)),
> node);
> - else if (PageTransHuge(page)) {
> + } else if (PageTransHuge(page)) {
> struct page *thp;
>
> - thp = alloc_pages_node(node,
> + thp = alloc_pages_node_keyid(node, page_keyid(page),
> (GFP_TRANSHUGE | __GFP_THISNODE),
> HPAGE_PMD_ORDER);
> if (!thp)
> return NULL;
> prep_transhuge_page(thp);
> return thp;
> - } else
> - return __alloc_pages_node(node, GFP_HIGHUSER_MOVABLE |
> - __GFP_THISNODE, 0);
> + } else {
> + return __alloc_pages_node_keyid(node, page_keyid(page),
> + GFP_HIGHUSER_MOVABLE | __GFP_THISNODE, 0);
> + }
> }
>
> /*
> @@ -2053,9 +2060,13 @@ alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
> {
> struct mempolicy *pol;
> struct page *page;
> - int preferred_nid;
> + bool deferred_zero;
> + int keyid, preferred_nid;
> nodemask_t *nmask;
>
> + keyid = vma_keyid(vma);
> + deferred_zero = deferred_page_zero(keyid, &gfp);
> +
> pol = get_vma_policy(vma, addr);
>
> if (pol->mode == MPOL_INTERLEAVE) {
> @@ -2097,6 +2108,8 @@ 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)
> + prep_encrypted_page(page, order, keyid, deferred_zero);
> return page;
> }
>
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 663a5449367a..04b36a56865d 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1880,7 +1880,7 @@ 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) &
> @@ -2006,7 +2006,7 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm,
> int page_lru = page_is_file_cache(page);
> unsigned long start = address & HPAGE_PMD_MASK;
>
> - new_page = alloc_pages_node(node,
> + new_page = alloc_pages_node_keyid(node, page_keyid(page),
> (GFP_TRANSHUGE_LIGHT | __GFP_THISNODE),
> HPAGE_PMD_ORDER);
> if (!new_page)
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index c02cff1ed56e..ab1d8661aa87 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3930,6 +3930,41 @@ should_compact_retry(struct alloc_context *ac, unsigned int order, int alloc_fla
> }
> #endif /* CONFIG_COMPACTION */
>
> +#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)
> +{

Having NUMA and !NUMA alloc_pages_vma() in different place is confusing,
but I don't have a better suggestion :(

> + struct page *page;
> + bool deferred_zero;
> + int keyid = vma_keyid(vma);
> +
> + deferred_zero = deferred_page_zero(keyid, &gfp_mask);
> + page = alloc_pages(gfp_mask, order);
> + if (page)
> + prep_encrypted_page(page, order, keyid, deferred_zero);
> +
> + return page;
> +}
> +#endif
> +
> +struct page * __alloc_pages_node_keyid(int nid, int keyid,
> + gfp_t gfp_mask, unsigned int order)
> +{

A kerneldoc description would be appreciated

> + struct page *page;
> + bool deferred_zero;
> +
> + VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES);
> + VM_WARN_ON(!node_online(nid));
> +
> + deferred_zero = deferred_page_zero(keyid, &gfp_mask);
> + page = __alloc_pages(gfp_mask, order, nid);
> + if (page)
> + prep_encrypted_page(page, order, keyid, deferred_zero);
> +
> + return page;
> +}

Shouldn't it be EXPORT_SYMBOL?

> +
> #ifdef CONFIG_LOCKDEP
> static struct lockdep_map __fs_reclaim_map =
> STATIC_LOCKDEP_MAP_INIT("fs_reclaim", &__fs_reclaim_map);
> @@ -4645,6 +4680,21 @@ __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)
> +{

A kerneldoc description would be appreciated

> + struct page *page;
> + bool deferred_zero;
> +
> + deferred_zero = deferred_page_zero(keyid, &gfp_mask);
> + page = __alloc_pages_nodemask(gfp_mask, order, preferred_nid, nodemask);
> + if (page)
> + prep_encrypted_page(page, order, keyid, deferred_zero);
> + return page;
> +}
> +EXPORT_SYMBOL(__alloc_pages_nodemask_keyid);
> +
> /*
> * Common helper functions. Never use with __GFP_HIGHMEM because the returned
> * address cannot represent highmem pages. Use alloc_pages and then kmap if
> --
> 2.20.1
>

--
Sincerely yours,
Mike.

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