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Subject[HMM v13 06/18] mm/ZONE_DEVICE/unaddressable: add special swap for unaddressable
Date
To allow use of device un-addressable memory inside a process add a
special swap type. Also add a new callback to handle page fault on
such entry.

Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
---
fs/proc/task_mmu.c | 10 +++++++-
include/linux/memremap.h | 5 ++++
include/linux/swap.h | 18 ++++++++++---
include/linux/swapops.h | 67 ++++++++++++++++++++++++++++++++++++++++++++++++
kernel/memremap.c | 14 ++++++++++
mm/Kconfig | 12 +++++++++
mm/memory.c | 24 +++++++++++++++++
mm/mprotect.c | 12 +++++++++
8 files changed, 158 insertions(+), 4 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 6909582..0726d39 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -544,8 +544,11 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
} else {
mss->swap_pss += (u64)PAGE_SIZE << PSS_SHIFT;
}
- } else if (is_migration_entry(swpent))
+ } else if (is_migration_entry(swpent)) {
page = migration_entry_to_page(swpent);
+ } else if (is_device_entry(swpent)) {
+ page = device_entry_to_page(swpent);
+ }
} else if (unlikely(IS_ENABLED(CONFIG_SHMEM) && mss->check_shmem_swap
&& pte_none(*pte))) {
page = find_get_entry(vma->vm_file->f_mapping,
@@ -708,6 +711,8 @@ static int smaps_hugetlb_range(pte_t *pte, unsigned long hmask,

if (is_migration_entry(swpent))
page = migration_entry_to_page(swpent);
+ if (is_device_entry(swpent))
+ page = device_entry_to_page(swpent);
}
if (page) {
int mapcount = page_mapcount(page);
@@ -1191,6 +1196,9 @@ static pagemap_entry_t pte_to_pagemap_entry(struct pagemapread *pm,
flags |= PM_SWAP;
if (is_migration_entry(entry))
page = migration_entry_to_page(entry);
+
+ if (is_device_entry(entry))
+ page = device_entry_to_page(entry);
}

if (page && !PageAnon(page))
diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index b6f03e9..d584c74 100644
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -47,6 +47,11 @@ static inline struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start)
*/
struct dev_pagemap {
void (*free_devpage)(struct page *page, void *data);
+ int (*fault)(struct vm_area_struct *vma,
+ unsigned long addr,
+ struct page *page,
+ unsigned flags,
+ pmd_t *pmdp);
struct vmem_altmap *altmap;
const struct resource *res;
struct percpu_ref *ref;
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 7e553e1..599cb54 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -50,6 +50,17 @@ static inline int current_is_kswapd(void)
*/

/*
+ * Un-addressable device memory support
+ */
+#ifdef CONFIG_DEVICE_UNADDRESSABLE
+#define SWP_DEVICE_NUM 2
+#define SWP_DEVICE_WRITE (MAX_SWAPFILES + SWP_HWPOISON_NUM + SWP_MIGRATION_NUM)
+#define SWP_DEVICE (MAX_SWAPFILES + SWP_HWPOISON_NUM + SWP_MIGRATION_NUM + 1)
+#else
+#define SWP_DEVICE_NUM 0
+#endif
+
+/*
* NUMA node memory migration support
*/
#ifdef CONFIG_MIGRATION
@@ -71,7 +82,8 @@ static inline int current_is_kswapd(void)
#endif

#define MAX_SWAPFILES \
- ((1 << MAX_SWAPFILES_SHIFT) - SWP_MIGRATION_NUM - SWP_HWPOISON_NUM)
+ ((1 << MAX_SWAPFILES_SHIFT) - SWP_DEVICE_NUM - \
+ SWP_MIGRATION_NUM - SWP_HWPOISON_NUM)

/*
* Magic header for a swap area. The first part of the union is
@@ -442,8 +454,8 @@ static inline void show_swap_cache_info(void)
{
}

-#define free_swap_and_cache(swp) is_migration_entry(swp)
-#define swapcache_prepare(swp) is_migration_entry(swp)
+#define free_swap_and_cache(e) (is_migration_entry(e) || is_device_entry(e))
+#define swapcache_prepare(e) (is_migration_entry(e) || is_device_entry(e))

static inline int add_swap_count_continuation(swp_entry_t swp, gfp_t gfp_mask)
{
diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index 5c3a5f3..d1aa425 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -100,6 +100,73 @@ static inline void *swp_to_radix_entry(swp_entry_t entry)
return (void *)(value | RADIX_TREE_EXCEPTIONAL_ENTRY);
}

+#ifdef CONFIG_DEVICE_UNADDRESSABLE
+static inline swp_entry_t make_device_entry(struct page *page, bool write)
+{
+ return swp_entry(write?SWP_DEVICE_WRITE:SWP_DEVICE, page_to_pfn(page));
+}
+
+static inline bool is_device_entry(swp_entry_t entry)
+{
+ int type = swp_type(entry);
+ return type == SWP_DEVICE || type == SWP_DEVICE_WRITE;
+}
+
+static inline void make_device_entry_read(swp_entry_t *entry)
+{
+ *entry = swp_entry(SWP_DEVICE, swp_offset(*entry));
+}
+
+static inline bool is_write_device_entry(swp_entry_t entry)
+{
+ return unlikely(swp_type(entry) == SWP_DEVICE_WRITE);
+}
+
+static inline struct page *device_entry_to_page(swp_entry_t entry)
+{
+ return pfn_to_page(swp_offset(entry));
+}
+
+int device_entry_fault(struct vm_area_struct *vma,
+ unsigned long addr,
+ swp_entry_t entry,
+ unsigned flags,
+ pmd_t *pmdp);
+#else /* CONFIG_DEVICE_UNADDRESSABLE */
+static inline swp_entry_t make_device_entry(struct page *page, bool write)
+{
+ return swp_entry(0, 0);
+}
+
+static inline void make_device_entry_read(swp_entry_t *entry)
+{
+}
+
+static inline bool is_device_entry(swp_entry_t entry)
+{
+ return false;
+}
+
+static inline bool is_write_device_entry(swp_entry_t entry)
+{
+ return false;
+}
+
+static inline struct page *device_entry_to_page(swp_entry_t entry)
+{
+ return NULL;
+}
+
+static inline int device_entry_fault(struct vm_area_struct *vma,
+ unsigned long addr,
+ swp_entry_t entry,
+ unsigned flags,
+ pmd_t *pmdp)
+{
+ return VM_FAULT_SIGBUS;
+}
+#endif /* CONFIG_DEVICE_UNADDRESSABLE */
+
#ifdef CONFIG_MIGRATION
static inline swp_entry_t make_migration_entry(struct page *page, int write)
{
diff --git a/kernel/memremap.c b/kernel/memremap.c
index cf83928..0670015 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -18,6 +18,8 @@
#include <linux/io.h>
#include <linux/mm.h>
#include <linux/memory_hotplug.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>

#ifndef ioremap_cache
/* temporary while we convert existing ioremap_cache users to memremap */
@@ -200,6 +202,18 @@ void put_zone_device_page(struct page *page)
}
EXPORT_SYMBOL(put_zone_device_page);

+int device_entry_fault(struct vm_area_struct *vma,
+ unsigned long addr,
+ swp_entry_t entry,
+ unsigned flags,
+ pmd_t *pmdp)
+{
+ struct page *page = device_entry_to_page(entry);
+
+ return page->pgmap->fault(vma, addr, page, flags, pmdp);
+}
+EXPORT_SYMBOL(device_entry_fault);
+
static void pgmap_radix_release(struct resource *res)
{
resource_size_t key, align_start, align_size, align_end;
diff --git a/mm/Kconfig b/mm/Kconfig
index be0ee11..0a21411 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -704,6 +704,18 @@ config ZONE_DEVICE

If FS_DAX is enabled, then say Y.

+config DEVICE_UNADDRESSABLE
+ bool "Un-addressable device memory (GPU memory, ...)"
+ depends on ZONE_DEVICE
+
+ help
+ Allow to create struct page for un-addressable device memory
+ ie memory that is only accessible by the device (or group of
+ devices).
+
+ This allow to migrate chunk of process memory to device memory
+ while that memory is use by the device.
+
config FRAME_VECTOR
bool

diff --git a/mm/memory.c b/mm/memory.c
index 15f2908..a83d690 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -889,6 +889,21 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
pte = pte_swp_mksoft_dirty(pte);
set_pte_at(src_mm, addr, src_pte, pte);
}
+ } else if (is_device_entry(entry)) {
+ page = device_entry_to_page(entry);
+
+ get_page(page);
+ rss[mm_counter(page)]++;
+ page_dup_rmap(page, false);
+
+ if (is_write_device_entry(entry) &&
+ is_cow_mapping(vm_flags)) {
+ make_device_entry_read(&entry);
+ pte = swp_entry_to_pte(entry);
+ if (pte_swp_soft_dirty(*src_pte))
+ pte = pte_swp_mksoft_dirty(pte);
+ set_pte_at(src_mm, addr, src_pte, pte);
+ }
}
goto out_set_pte;
}
@@ -1191,6 +1206,12 @@ again:

page = migration_entry_to_page(entry);
rss[mm_counter(page)]--;
+ } else if (is_device_entry(entry)) {
+ struct page *page = device_entry_to_page(entry);
+ rss[mm_counter(page)]--;
+
+ page_remove_rmap(page, false);
+ put_page(page);
}
if (unlikely(!free_swap_and_cache(entry)))
print_bad_pte(vma, addr, ptent, NULL);
@@ -2536,6 +2557,9 @@ int do_swap_page(struct fault_env *fe, pte_t orig_pte)
if (unlikely(non_swap_entry(entry))) {
if (is_migration_entry(entry)) {
migration_entry_wait(vma->vm_mm, fe->pmd, fe->address);
+ } else if (is_device_entry(entry)) {
+ ret = device_entry_fault(vma, fe->address, entry,
+ fe->flags, fe->pmd);
} else if (is_hwpoison_entry(entry)) {
ret = VM_FAULT_HWPOISON;
} else {
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 1bc1eb3..70aff3a 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -139,6 +139,18 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,

pages++;
}
+
+ if (is_write_device_entry(entry)) {
+ pte_t newpte;
+
+ make_device_entry_read(&entry);
+ newpte = swp_entry_to_pte(entry);
+ if (pte_swp_soft_dirty(oldpte))
+ newpte = pte_swp_mksoft_dirty(newpte);
+ set_pte_at(mm, addr, pte, newpte);
+
+ pages++;
+ }
}
} while (pte++, addr += PAGE_SIZE, addr != end);
arch_leave_lazy_mmu_mode();
--
2.4.3
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