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Date: Fri, 7 Apr 2017 16:28:51 -0400
From: Jérôme Glisse <jglisse@...hat.com>
To: linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc: John Hubbard <jhubbard@...dia.com>,
Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
Balbir Singh <balbir@....ibm.com>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Aneesh Kumar <aneesh.kumar@...ux.vnet.ibm.com>,
"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
Haren Myneni <haren@...ux.vnet.ibm.com>,
Dan Williams <dan.j.williams@...el.com>,
Jérôme Glisse <jglisse@...hat.com>
Subject: [RFC HMM CDM 1/3] mm/cache-coherent-device-memory: new type of ZONE_DEVICE
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.
Signed-off-by: Jérôme Glisse <jglisse@...hat.com>
---
include/linux/ioport.h | 1 +
include/linux/memory_hotplug.h | 8 ++++++++
include/linux/memremap.h | 26 ++++++++++++++++++++++++++
mm/Kconfig | 9 +++++++++
mm/gup.c | 1 +
mm/memcontrol.c | 25 +++++++++++++++++++++++--
mm/memory.c | 18 ++++++++++++++++++
mm/migrate.c | 12 +++++++++++-
8 files changed, 97 insertions(+), 3 deletions(-)
diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index ec619dc..55cba87 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_MEMORY_UNADDRESSABLE = 6,
+ IORES_DESC_DEVICE_MEMORY_CACHE_COHERENT = 7,
};
/* helpers to define resources */
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index e60f203..7c587ce 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -36,11 +36,19 @@ struct resource;
* page must be treated as an opaque object, rather than a "normal" struct page.
* A more complete discussion of unaddressable memory may be found in
* include/linux/hmm.h and Documentation/vm/hmm.txt.
+ *
+ * MEMORY_DEVICE_CACHE_COHERENT:
+ * 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_NORMAL = 0,
MEMORY_DEVICE_PERSISTENT,
MEMORY_DEVICE_UNADDRESSABLE,
+ MEMORY_DEVICE_CACHE_COHERENT,
};
#ifdef CONFIG_MEMORY_HOTPLUG
diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index 3a9494e..6029ddf 100644
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -41,6 +41,8 @@ static inline struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start)
* page_fault()
* page_free()
*
+ * For MEMORY_DEVICE_CACHE_COHERENT only the page_free() callback matter.
+ *
* Additional notes about MEMORY_DEVICE_UNADDRESSABLE may be found in
* include/linux/hmm.h and Documentation/vm/hmm.txt. There is also a brief
* explanation in include/linux/memory_hotplug.h.
@@ -99,12 +101,26 @@ void *devm_memremap_pages(struct device *dev, struct resource *res,
struct percpu_ref *ref, struct vmem_altmap *altmap);
struct dev_pagemap *find_dev_pagemap(resource_size_t phys);
+static inline bool is_device_persistent_page(const struct page *page)
+{
+ /* See MEMORY_DEVICE_UNADDRESSABLE in include/linux/memory_hotplug.h */
+ return ((page_zonenum(page) == ZONE_DEVICE) &&
+ (page->pgmap->type == MEMORY_DEVICE_PERSISTENT));
+}
+
static inline bool is_device_unaddressable_page(const struct page *page)
{
/* See MEMORY_DEVICE_UNADDRESSABLE in include/linux/memory_hotplug.h */
return ((page_zonenum(page) == ZONE_DEVICE) &&
(page->pgmap->type == MEMORY_DEVICE_UNADDRESSABLE));
}
+
+static inline bool is_device_cache_coherent_page(const struct page *page)
+{
+ /* See MEMORY_DEVICE_UNADDRESSABLE in include/linux/memory_hotplug.h */
+ return ((page_zonenum(page) == ZONE_DEVICE) &&
+ (page->pgmap->type == MEMORY_DEVICE_CACHE_COHERENT));
+}
#else
static inline void *devm_memremap_pages(struct device *dev,
struct resource *res, struct percpu_ref *ref,
@@ -124,10 +140,20 @@ static inline struct dev_pagemap *find_dev_pagemap(resource_size_t phys)
return NULL;
}
+static inline bool is_device_persistent_page(const struct page *page)
+{
+ return false;
+}
+
static inline bool is_device_unaddressable_page(const struct page *page)
{
return false;
}
+
+static inline bool is_device_cache_coherent_page(const struct page *page)
+{
+ return false;
+}
#endif
/**
diff --git a/mm/Kconfig b/mm/Kconfig
index 96dcf61..5c7b0ec 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -744,6 +744,15 @@ config DEVICE_UNADDRESSABLE
i.e., memory that is only accessible from the device (or group of
devices).
+config DEVICE_CACHE_COHERENT
+ bool "Cache coherent device memory (GPU memory, ...)"
+ depends on ZONE_DEVICE
+
+ help
+ Allow to create struct page for cache-coherent device memory
+ which is only do-able with advance system bus like CAPI or
+ CCIX.
+
config FRAME_VECTOR
bool
diff --git a/mm/gup.c b/mm/gup.c
index 4039ec2..4d54220 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -121,6 +121,7 @@ static struct page *follow_page_pte(struct vm_area_struct *vma,
page = pte_page(pte);
else
goto no_page;
+ pgmap = get_dev_pagemap(pte_pfn(pte), NULL);
} else if (unlikely(!page)) {
if (flags & FOLL_DUMP) {
/* Avoid special (like zero) pages in core dumps */
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 712a687..fd188cf 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4388,6 +4388,7 @@ enum mc_target_type {
MC_TARGET_NONE = 0,
MC_TARGET_PAGE,
MC_TARGET_SWAP,
+ MC_TARGET_DEVICE,
};
static struct page *mc_handle_present_pte(struct vm_area_struct *vma,
@@ -4395,8 +4396,22 @@ static struct page *mc_handle_present_pte(struct vm_area_struct *vma,
{
struct page *page = vm_normal_page(vma, addr, ptent);
- if (!page || !page_mapped(page))
+ if (!page || !page_mapped(page)) {
+ if (pte_devmap(pte)) {
+ struct dev_pagemap *pgmap = NULL;
+
+ page = pte_page(ptent);
+ if (!is_device_cache_coherent_page(page))
+ return NULL;
+
+ pgmap = get_dev_pagemap(pte_pfn(pte), NULL);
+ if (pgmap) {
+ get_page(page);
+ return page;
+ }
+ }
return NULL;
+ }
if (PageAnon(page)) {
if (!(mc.flags & MOVE_ANON))
return NULL;
@@ -4611,6 +4626,8 @@ static enum mc_target_type get_mctgt_type(struct vm_area_struct *vma,
*/
if (page->mem_cgroup == mc.from) {
ret = MC_TARGET_PAGE;
+ if (is_device_cache_coherent_page(page))
+ ret = MC_TARGET_DEVICE;
if (target)
target->page = page;
}
@@ -4896,12 +4913,16 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
for (; addr != end; addr += PAGE_SIZE) {
pte_t ptent = *(pte++);
+ bool device = false;
swp_entry_t ent;
if (!mc.precharge)
break;
switch (get_mctgt_type(vma, addr, ptent, &target)) {
+ case MC_TARGET_DEVICE:
+ device = true;
+ /* fall through */
case MC_TARGET_PAGE:
page = target.page;
/*
@@ -4912,7 +4933,7 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
*/
if (PageTransCompound(page))
goto put;
- if (isolate_lru_page(page))
+ if (!device && isolate_lru_page(page))
goto put;
if (!mem_cgroup_move_account(page, false,
mc.from, mc.to)) {
diff --git a/mm/memory.c b/mm/memory.c
index d68c653..bf41258 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -979,6 +979,24 @@ 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)) {
+ struct dev_pagemap *pgmap = NULL;
+
+ 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_cache_coherent_page(page)) {
+ pgmap = get_dev_pagemap(pte_pfn(pte), NULL);
+ if (pgmap) {
+ get_page(page);
+ page_dup_rmap(page, false);
+ rss[mm_counter(page)]++;
+ }
+ }
}
out_set_pte:
diff --git a/mm/migrate.c b/mm/migrate.c
index cbaa4f2..2497357 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -241,6 +241,9 @@ static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma,
pte = swp_entry_to_pte(entry);
if (pte_swp_soft_dirty(*pvmw.pte))
pte = pte_mksoft_dirty(pte);
+ } else if (is_device_cache_coherent_page(new)) {
+ pte = pte_mkdevmap(pte);
+ flush_dcache_page(new);
} else
flush_dcache_page(new);
set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte);
@@ -2300,7 +2303,8 @@ 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_unaddressable_page(page)) {
+ if (is_device_unaddressable_page(page) ||
+ is_device_cache_coherent_page(page)) {
extra++;
} else
/* Other ZONE_DEVICE memory type are not supported */
@@ -2617,6 +2621,12 @@ static void migrate_vma_pages(struct migrate_vma *migrate)
migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;
continue;
}
+ } else if (is_device_cache_coherent_page(newpage)) {
+ /*
+ * Anything can be migrated to a device cache
+ * coherent page.
+ */
+ continue;
} else {
/*
* Other types of ZONE_DEVICE page are not
--
2.7.4
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