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Subject[PATCH 2/5] mm/device-public-memory: device memory cache coherent with CPU v2
Date
Platform with advance system bus (like CAPI or CCIX) allow device
memory to be accessible from CPU in a cache coherent fashion. Add
a new type of ZONE_DEVICE to represent such memory. The use case
are the same as for the un-addressable device memory but without
all the corners cases.

Changed since v1:
- Kconfig and #if/#else cleanup

Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Cc: Balbir Singh <balbirs@au1.ibm.com>
Cc: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
---
fs/proc/task_mmu.c | 2 +-
include/linux/hmm.h | 4 ++--
include/linux/ioport.h | 1 +
include/linux/memremap.h | 21 +++++++++++++++++
include/linux/mm.h | 16 ++++++++-----
kernel/memremap.c | 11 ++++++---
mm/Kconfig | 11 +++++++++
mm/gup.c | 7 ++++++
mm/hmm.c | 4 ++--
mm/madvise.c | 2 +-
mm/memory.c | 46 +++++++++++++++++++++++++++++++++----
mm/migrate.c | 60 ++++++++++++++++++++++++++++++++----------------
mm/swap.c | 11 +++++++++
13 files changed, 156 insertions(+), 40 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 957b6ea80d5f..1f38f2c7cc34 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1182,7 +1182,7 @@ static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm,
if (pm->show_pfn)
frame = pte_pfn(pte);
flags |= PM_PRESENT;
- page = vm_normal_page(vma, addr, pte);
+ page = _vm_normal_page(vma, addr, pte, true);
if (pte_soft_dirty(pte))
flags |= PM_SOFT_DIRTY;
} else if (is_swap_pte(pte)) {
diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index 458d0d6d82f3..a40288309fd2 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -327,7 +327,7 @@ int hmm_vma_fault(struct vm_area_struct *vma,
#endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */


-#if IS_ENABLED(CONFIG_DEVICE_PRIVATE)
+#if IS_ENABLED(CONFIG_DEVICE_PRIVATE) || IS_ENABLED(CONFIG_DEVICE_PUBLIC)
struct hmm_devmem;

struct page *hmm_vma_alloc_locked_page(struct vm_area_struct *vma,
@@ -443,7 +443,7 @@ struct hmm_device {
*/
struct hmm_device *hmm_device_new(void *drvdata);
void hmm_device_put(struct hmm_device *hmm_device);
-#endif /* IS_ENABLED(CONFIG_DEVICE_PRIVATE) */
+#endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */


/* Below are for HMM internal use only! Not to be used by device driver! */
diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index 3a4f69137bc2..f5cf32e80041 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -131,6 +131,7 @@ enum {
IORES_DESC_PERSISTENT_MEMORY = 4,
IORES_DESC_PERSISTENT_MEMORY_LEGACY = 5,
IORES_DESC_DEVICE_PRIVATE_MEMORY = 6,
+ IORES_DESC_DEVICE_PUBLIC_MEMORY = 7,
};

/* helpers to define resources */
diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index 2299cc2d387d..916ca1653ced 100644
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -57,10 +57,18 @@ static inline struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start)
*
* A more complete discussion of unaddressable memory may be found in
* include/linux/hmm.h and Documentation/vm/hmm.txt.
+ *
+ * MEMORY_DEVICE_PUBLIC:
+ * Device memory that is cache coherent from device and CPU point of view. This
+ * is use on platform that have an advance system bus (like CAPI or CCIX). A
+ * driver can hotplug the device memory using ZONE_DEVICE and with that memory
+ * type. Any page of a process can be migrated to such memory. However no one
+ * should be allow to pin such memory so that it can always be evicted.
*/
enum memory_type {
MEMORY_DEVICE_PERSISTENT = 0,
MEMORY_DEVICE_PRIVATE,
+ MEMORY_DEVICE_PUBLIC,
};

/*
@@ -92,6 +100,8 @@ enum memory_type {
* The page_free() callback is called once the page refcount reaches 1
* (ZONE_DEVICE pages never reach 0 refcount unless there is a refcount bug.
* This allows the device driver to implement its own memory management.)
+ *
+ * For MEMORY_DEVICE_CACHE_COHERENT only the page_free() callback matter.
*/
typedef int (*dev_page_fault_t)(struct vm_area_struct *vma,
unsigned long addr,
@@ -134,6 +144,12 @@ static inline bool is_device_private_page(const struct page *page)
return is_zone_device_page(page) &&
page->pgmap->type == MEMORY_DEVICE_PRIVATE;
}
+
+static inline bool is_device_public_page(const struct page *page)
+{
+ return is_zone_device_page(page) &&
+ page->pgmap->type == MEMORY_DEVICE_PUBLIC;
+}
#else
static inline void *devm_memremap_pages(struct device *dev,
struct resource *res, struct percpu_ref *ref,
@@ -157,6 +173,11 @@ static inline bool is_device_private_page(const struct page *page)
{
return false;
}
+
+static inline bool is_device_public_page(const struct page *page)
+{
+ return false;
+}
#endif

/**
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 330a216ac315..8b72b122de93 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -797,14 +797,15 @@ static inline bool is_zone_device_page(const struct page *page)
#endif

#ifdef CONFIG_DEVICE_PRIVATE
-void put_zone_device_private_page(struct page *page);
+void put_zone_device_private_or_public_page(struct page *page);
#else
-static inline void put_zone_device_private_page(struct page *page)
+static inline void put_zone_device_private_or_public_page(struct page *page)
{
}
#endif

static inline bool is_device_private_page(const struct page *page);
+static inline bool is_device_public_page(const struct page *page);

DECLARE_STATIC_KEY_FALSE(device_private_key);

@@ -830,8 +831,9 @@ static inline void put_page(struct page *page)
* include/linux/memremap.h and HMM for details.
*/
if (static_branch_unlikely(&device_private_key) &&
- unlikely(is_device_private_page(page))) {
- put_zone_device_private_page(page);
+ unlikely(is_device_private_page(page) ||
+ is_device_public_page(page))) {
+ put_zone_device_private_or_public_page(page);
return;
}

@@ -1220,8 +1222,10 @@ struct zap_details {
pgoff_t last_index; /* Highest page->index to unmap */
};

-struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
- pte_t pte);
+struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
+ pte_t pte, bool with_public_device);
+#define vm_normal_page(vma, addr, pte) _vm_normal_page(vma, addr, pte, false)
+
struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
pmd_t pmd);

diff --git a/kernel/memremap.c b/kernel/memremap.c
index e82456c39a6a..da74775f2247 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -466,7 +466,7 @@ struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start)


#ifdef CONFIG_DEVICE_PRIVATE
-void put_zone_device_private_page(struct page *page)
+void put_zone_device_private_or_public_page(struct page *page)
{
int count = page_ref_dec_return(page);

@@ -474,10 +474,15 @@ void put_zone_device_private_page(struct page *page)
* If refcount is 1 then page is freed and refcount is stable as nobody
* holds a reference on the page.
*/
- if (count == 1)
+ if (count == 1) {
+ /* Clear Active bit in case of parallel mark_page_accessed */
+ __ClearPageActive(page);
+ __ClearPageWaiters(page);
+
page->pgmap->page_free(page, page->pgmap->data);
+ }
else if (!count)
__put_page(page);
}
-EXPORT_SYMBOL(put_zone_device_private_page);
+EXPORT_SYMBOL(put_zone_device_private_or_public_page);
#endif /* CONFIG_DEVICE_PRIVATE */
diff --git a/mm/Kconfig b/mm/Kconfig
index 3269ff1cc4cd..6002f1e40fcd 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -712,12 +712,23 @@ config ZONE_DEVICE
config DEVICE_PRIVATE
bool "Unaddressable device memory (GPU memory, ...)"
depends on ARCH_HAS_HMM
+ select HMM

help
Allows creation of struct pages to represent unaddressable device
memory; i.e., memory that is only accessible from the device (or
group of devices).

+config DEVICE_PUBLIC
+ bool "Addressable device memory (like GPU memory)"
+ depends on ARCH_HAS_HMM
+ select HMM
+
+ help
+ Allows creation of struct pages to represent addressable device
+ memory; i.e., memory that is accessible from both the device and
+ the CPU
+
config FRAME_VECTOR
bool

diff --git a/mm/gup.c b/mm/gup.c
index 23f01c40c88f..2f8e8604ff80 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -438,6 +438,13 @@ static int get_gate_page(struct mm_struct *mm, unsigned long address,
if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte)))
goto unmap;
*page = pte_page(*pte);
+
+ /*
+ * This should never happen (a device public page in the gate
+ * area).
+ */
+ if (is_device_public_page(*page))
+ goto unmap;
}
get_page(*page);
out:
diff --git a/mm/hmm.c b/mm/hmm.c
index 4e01c9ba9cc1..eadf70829c34 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -747,7 +747,7 @@ EXPORT_SYMBOL(hmm_vma_fault);
#endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */


-#if IS_ENABLED(CONFIG_DEVICE_PRIVATE)
+#if IS_ENABLED(CONFIG_DEVICE_PRIVATE) || IS_ENABLED(CONFIG_DEVICE_PUBLIC)
struct page *hmm_vma_alloc_locked_page(struct vm_area_struct *vma,
unsigned long addr)
{
@@ -1190,4 +1190,4 @@ static int __init hmm_init(void)
}

device_initcall(hmm_init);
-#endif /* IS_ENABLED(CONFIG_DEVICE_PRIVATE) */
+#endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */
diff --git a/mm/madvise.c b/mm/madvise.c
index 9976852f1e1c..197277156ce3 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -343,7 +343,7 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
continue;
}

- page = vm_normal_page(vma, addr, ptent);
+ page = _vm_normal_page(vma, addr, ptent, true);
if (!page)
continue;

diff --git a/mm/memory.c b/mm/memory.c
index 4fcdab3ec525..cee2bed01aa0 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -789,8 +789,8 @@ static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
#else
# define HAVE_PTE_SPECIAL 0
#endif
-struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
- pte_t pte)
+struct page *_vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
+ pte_t pte, bool with_public_device)
{
unsigned long pfn = pte_pfn(pte);

@@ -801,8 +801,31 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
return vma->vm_ops->find_special_page(vma, addr);
if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
return NULL;
- if (!is_zero_pfn(pfn))
- print_bad_pte(vma, addr, pte, NULL);
+ if (is_zero_pfn(pfn))
+ return NULL;
+
+ /*
+ * Device public pages are special pages (they are ZONE_DEVICE
+ * pages but different from persistent memory). They behave
+ * allmost like normal pages. The difference is that they are
+ * not on the lru and thus should never be involve with any-
+ * thing that involve lru manipulation (mlock, numa balancing,
+ * ...).
+ *
+ * This is why we still want to return NULL for such page from
+ * vm_normal_page() so that we do not have to special case all
+ * call site of vm_normal_page().
+ */
+ if (likely(pfn < highest_memmap_pfn)) {
+ struct page *page = pfn_to_page(pfn);
+
+ if (is_device_public_page(page)) {
+ if (with_public_device)
+ return page;
+ return NULL;
+ }
+ }
+ print_bad_pte(vma, addr, pte, NULL);
return NULL;
}

@@ -983,6 +1006,19 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
get_page(page);
page_dup_rmap(page, false);
rss[mm_counter(page)]++;
+ } else if (pte_devmap(pte)) {
+ page = pte_page(pte);
+
+ /*
+ * Cache coherent device memory behave like regular page and
+ * not like persistent memory page. For more informations see
+ * MEMORY_DEVICE_CACHE_COHERENT in memory_hotplug.h
+ */
+ if (is_device_public_page(page)) {
+ get_page(page);
+ page_dup_rmap(page, false);
+ rss[mm_counter(page)]++;
+ }
}

out_set_pte:
@@ -1236,7 +1272,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
if (pte_present(ptent)) {
struct page *page;

- page = vm_normal_page(vma, addr, ptent);
+ page = _vm_normal_page(vma, addr, ptent, true);
if (unlikely(details) && page) {
/*
* unmap_shared_mapping_pages() wants to
diff --git a/mm/migrate.c b/mm/migrate.c
index 643ea61ca9bb..f9ae57f0c7a1 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -229,12 +229,19 @@ static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma,
if (is_write_migration_entry(entry))
pte = maybe_mkwrite(pte, vma);

- if (unlikely(is_zone_device_page(new)) &&
- is_device_private_page(new)) {
- entry = make_device_private_entry(new, pte_write(pte));
- pte = swp_entry_to_pte(entry);
- if (pte_swp_soft_dirty(*pvmw.pte))
- pte = pte_mksoft_dirty(pte);
+ if (unlikely(is_zone_device_page(new))) {
+ if (is_device_private_page(new)) {
+ entry = make_device_private_entry(new, pte_write(pte));
+ pte = swp_entry_to_pte(entry);
+ if (pte_swp_soft_dirty(*pvmw.pte))
+ pte = pte_mksoft_dirty(pte);
+ }
+#if IS_ENABLED(CONFIG_DEVICE_PUBLIC)
+ else if (is_device_public_page(new)) {
+ pte = pte_mkdevmap(pte);
+ flush_dcache_page(new);
+ }
+#endif /* IS_ENABLED(CONFIG_DEVICE_PUBLIC) */
} else
flush_dcache_page(new);

@@ -408,12 +415,11 @@ int migrate_page_move_mapping(struct address_space *mapping,
void **pslot;

/*
- * ZONE_DEVICE pages have 1 refcount always held by their device
- *
- * Note that DAX memory will never reach that point as it does not have
- * the MEMORY_DEVICE_ALLOW_MIGRATE flag set (see memory_hotplug.h).
+ * Device public or private pages have an extra refcount as they are
+ * ZONE_DEVICE pages.
*/
- expected_count += is_zone_device_page(page);
+ expected_count += is_device_private_page(page);
+ expected_count += is_device_public_page(page);

if (!mapping) {
/* Anonymous page without mapping */
@@ -2087,7 +2093,6 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm,

#endif /* CONFIG_NUMA */

-
struct migrate_vma {
struct vm_area_struct *vma;
unsigned long *dst;
@@ -2186,7 +2191,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
if (is_write_device_private_entry(entry))
mpfn |= MIGRATE_PFN_WRITE;
} else {
- page = vm_normal_page(migrate->vma, addr, pte);
+ page = _vm_normal_page(migrate->vma, addr, pte, true);
mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
}
@@ -2311,13 +2316,18 @@ static bool migrate_vma_check_page(struct page *page)

/* Page from ZONE_DEVICE have one extra reference */
if (is_zone_device_page(page)) {
- if (is_device_private_page(page)) {
+ if (is_device_private_page(page) ||
+ is_device_public_page(page))
extra++;
- } else
+ else
/* Other ZONE_DEVICE memory type are not supported */
return false;
}

+ /* For file back page */
+ if (page_mapping(page))
+ extra += 1 + page_has_private(page);
+
if ((page_count(page) - extra) > page_mapcount(page))
return false;

@@ -2541,11 +2551,21 @@ static void migrate_vma_insert_page(struct migrate_vma *migrate,
*/
__SetPageUptodate(page);

- if (is_zone_device_page(page) && is_device_private_page(page)) {
- swp_entry_t swp_entry;
+ if (is_zone_device_page(page)) {
+ if (is_device_private_page(page)) {
+ swp_entry_t swp_entry;

- swp_entry = make_device_private_entry(page, vma->vm_flags & VM_WRITE);
- entry = swp_entry_to_pte(swp_entry);
+ swp_entry = make_device_private_entry(page, vma->vm_flags & VM_WRITE);
+ entry = swp_entry_to_pte(swp_entry);
+ }
+#if IS_ENABLED(CONFIG_DEVICE_PUBLIC)
+ else if (is_device_public_page(page)) {
+ entry = pte_mkold(mk_pte(page, READ_ONCE(vma->vm_page_prot)));
+ if (vma->vm_flags & VM_WRITE)
+ entry = pte_mkwrite(pte_mkdirty(entry));
+ entry = pte_mkdevmap(entry);
+ }
+#endif /* IS_ENABLED(CONFIG_DEVICE_PUBLIC) */
} else {
entry = mk_pte(page, vma->vm_page_prot);
if (vma->vm_flags & VM_WRITE)
@@ -2631,7 +2651,7 @@ static void migrate_vma_pages(struct migrate_vma *migrate)
migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
continue;
}
- } else {
+ } else if (!is_device_public_page(newpage)) {
/*
* Other types of ZONE_DEVICE page are not
* supported.
diff --git a/mm/swap.c b/mm/swap.c
index 4f44dbd7f780..212370d6cb23 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -760,6 +760,17 @@ void release_pages(struct page **pages, int nr, bool cold)
if (is_huge_zero_page(page))
continue;

+ /* Device public page can not be huge page */
+ if (is_device_public_page(page)) {
+ if (locked_pgdat) {
+ spin_unlock_irqrestore(&locked_pgdat->lru_lock,
+ flags);
+ locked_pgdat = NULL;
+ }
+ put_zone_device_private_or_public_page(page);
+ continue;
+ }
+
page = compound_head(page);
if (!put_page_testzero(page))
continue;
--
2.13.0
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