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Subject[HMM v13 08/18] mm/hmm: heterogeneous memory management (HMM for short)
Date
HMM provides 3 separate functionality :
- Mirroring: synchronize CPU page table and device page table
- Device memory: allocating struct page for device memory
- Migration: migrating regular memory to device memory

This patch introduces some common helpers and definitions to all of
those 3 functionality.

Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Signed-off-by: Jatin Kumar <jakumar@nvidia.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Mark Hairgrove <mhairgrove@nvidia.com>
Signed-off-by: Sherry Cheung <SCheung@nvidia.com>
Signed-off-by: Subhash Gutti <sgutti@nvidia.com>
---
MAINTAINERS | 7 +++
include/linux/hmm.h | 139 +++++++++++++++++++++++++++++++++++++++++++++++
include/linux/mm_types.h | 5 ++
kernel/fork.c | 2 +
mm/Kconfig | 11 ++++
mm/Makefile | 1 +
mm/hmm.c | 86 +++++++++++++++++++++++++++++
7 files changed, 251 insertions(+)
create mode 100644 include/linux/hmm.h
create mode 100644 mm/hmm.c

diff --git a/MAINTAINERS b/MAINTAINERS
index f593300..41cd63d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5582,6 +5582,13 @@ S: Supported
F: drivers/scsi/hisi_sas/
F: Documentation/devicetree/bindings/scsi/hisilicon-sas.txt

+HMM - Heterogeneous Memory Management
+M: Jérôme Glisse <jglisse@redhat.com>
+L: linux-mm@kvack.org
+S: Maintained
+F: mm/hmm*
+F: include/linux/hmm*
+
HOST AP DRIVER
M: Jouni Malinen <j@w1.fi>
L: hostap@shmoo.com (subscribers-only)
diff --git a/include/linux/hmm.h b/include/linux/hmm.h
new file mode 100644
index 0000000..54dd529
--- /dev/null
+++ b/include/linux/hmm.h
@@ -0,0 +1,139 @@
+/*
+ * Copyright 2013 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * Authors: Jérôme Glisse <jglisse@redhat.com>
+ */
+/*
+ * HMM provides 3 separate functionality :
+ * - Mirroring: synchronize CPU page table and device page table
+ * - Device memory: allocating struct page for device memory
+ * - Migration: migrating regular memory to device memory
+ *
+ * Each can be use independently from the others.
+ *
+ *
+ * Mirroring:
+ *
+ * HMM provide helpers to mirror process address space on a device. For this it
+ * provides several helpers to order device page table update in respect to CPU
+ * page table update. Requirement is that for any given virtual address the CPU
+ * and device page table can not point to different physical page. It uses the
+ * mmu_notifier API and introduce virtual address range lock which block CPU
+ * page table update for a range while the device page table is being updated.
+ * Usage pattern is:
+ *
+ * hmm_vma_range_lock(vma, start, end);
+ * // snap shot CPU page table
+ * // update device page table from snapshot
+ * hmm_vma_range_unlock(vma, start, end);
+ *
+ * Any CPU page table update that conflict with a range lock will wait until
+ * range is unlock. This garanty proper serialization of CPU and device page
+ * table update.
+ *
+ *
+ * Device memory:
+ *
+ * HMM provides helpers to help leverage device memory either addressable like
+ * regular memory by the CPU or un-addressable at all. In both case the device
+ * memory is associated to dedicated structs page (which are allocated like for
+ * hotplug memory). Device memory management is under the responsability of the
+ * device driver. HMM only allocate and initialize the struct pages associated
+ * with the device memory.
+ *
+ * Allocating struct page for device memory allow to use device memory allmost
+ * like any regular memory. Unlike regular memory it can not be added to the
+ * lru, nor can any memory allocation can use device memory directly. Device
+ * memory will only end up to be use in a process if device driver migrate some
+ * of the process memory from regular memory to device memory.
+ *
+ *
+ * Migration:
+ *
+ * Existing memory migration mechanism (mm/migrate.c) does not allow to use
+ * something else than the CPU to copy from source to destination memory. More
+ * over existing code is not tailor to drive migration from process virtual
+ * address rather than from list of pages. Finaly the migration flow does not
+ * allow for graceful failure at different step of the migration process.
+ *
+ * HMM solves all of the above though simple API :
+ *
+ * hmm_vma_migrate(vma, start, end, ops);
+ *
+ * With ops struct providing 2 callback alloc_and_copy() which allocated the
+ * destination memory and initialize it using source memory. Migration can fail
+ * after this step and thus last callback finalize_and_map() allow the device
+ * driver to know which page were successfully migrated and which were not.
+ *
+ * This can easily be use outside of HMM intended use case.
+ *
+ *
+ * This header file contain all the API related to this 3 functionality and
+ * each functions and struct are more thouroughly documented in below comments.
+ */
+#ifndef LINUX_HMM_H
+#define LINUX_HMM_H
+
+#include <linux/kconfig.h>
+
+#if IS_ENABLED(CONFIG_HMM)
+
+
+/*
+ * hmm_pfn_t - HMM use its own pfn type to keep several flags per page
+ *
+ * Flags:
+ * HMM_PFN_VALID: pfn is valid
+ * HMM_PFN_WRITE: CPU page table have the write permission set
+ */
+typedef unsigned long hmm_pfn_t;
+
+#define HMM_PFN_VALID (1 << 0)
+#define HMM_PFN_WRITE (1 << 1)
+#define HMM_PFN_SHIFT 2
+
+static inline struct page *hmm_pfn_to_page(hmm_pfn_t pfn)
+{
+ if (!(pfn & HMM_PFN_VALID))
+ return NULL;
+ return pfn_to_page(pfn >> HMM_PFN_SHIFT);
+}
+
+static inline unsigned long hmm_pfn_to_pfn(hmm_pfn_t pfn)
+{
+ if (!(pfn & HMM_PFN_VALID))
+ return -1UL;
+ return (pfn >> HMM_PFN_SHIFT);
+}
+
+static inline hmm_pfn_t hmm_pfn_from_page(struct page *page)
+{
+ return (page_to_pfn(page) << HMM_PFN_SHIFT) | HMM_PFN_VALID;
+}
+
+static inline hmm_pfn_t hmm_pfn_from_pfn(unsigned long pfn)
+{
+ return (pfn << HMM_PFN_SHIFT) | HMM_PFN_VALID;
+}
+
+
+/* Below are for HMM internal use only ! Not to be use by device driver ! */
+void hmm_mm_destroy(struct mm_struct *mm);
+
+#else /* IS_ENABLED(CONFIG_HMM) */
+
+/* Below are for HMM internal use only ! Not to be use by device driver ! */
+static inline void hmm_mm_destroy(struct mm_struct *mm) {}
+
+#endif /* IS_ENABLED(CONFIG_HMM) */
+#endif /* LINUX_HMM_H */
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 4a8aced..4effdbf 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -23,6 +23,7 @@

struct address_space;
struct mem_cgroup;
+struct hmm;

#define USE_SPLIT_PTE_PTLOCKS (NR_CPUS >= CONFIG_SPLIT_PTLOCK_CPUS)
#define USE_SPLIT_PMD_PTLOCKS (USE_SPLIT_PTE_PTLOCKS && \
@@ -516,6 +517,10 @@ struct mm_struct {
atomic_long_t hugetlb_usage;
#endif
struct work_struct async_put_work;
+#if IS_ENABLED(CONFIG_HMM)
+ /* HMM need to track few things per mm */
+ struct hmm *hmm;
+#endif
};

static inline void mm_init_cpumask(struct mm_struct *mm)
diff --git a/kernel/fork.c b/kernel/fork.c
index 690a1aad..af0eec8 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -27,6 +27,7 @@
#include <linux/binfmts.h>
#include <linux/mman.h>
#include <linux/mmu_notifier.h>
+#include <linux/hmm.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/vmacache.h>
@@ -702,6 +703,7 @@ void __mmdrop(struct mm_struct *mm)
BUG_ON(mm == &init_mm);
mm_free_pgd(mm);
destroy_context(mm);
+ hmm_mm_destroy(mm);
mmu_notifier_mm_destroy(mm);
check_mm(mm);
free_mm(mm);
diff --git a/mm/Kconfig b/mm/Kconfig
index 0a21411..be18cc2 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -289,6 +289,17 @@ config MIGRATION
config ARCH_ENABLE_HUGEPAGE_MIGRATION
bool

+config HMM
+ bool "Heterogeneous memory management (HMM)"
+ depends on MMU
+ default n
+ help
+ Heterogeneous memory management, set of helpers for:
+ - mirroring of process address space on a device
+ - using device memory transparently inside a process
+
+ If unsure, say N to disable HMM.
+
config PHYS_ADDR_T_64BIT
def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT

diff --git a/mm/Makefile b/mm/Makefile
index 2ca1faf..6ac1284 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -76,6 +76,7 @@ obj-$(CONFIG_FAILSLAB) += failslab.o
obj-$(CONFIG_MEMORY_HOTPLUG) += memory_hotplug.o
obj-$(CONFIG_MEMTEST) += memtest.o
obj-$(CONFIG_MIGRATION) += migrate.o
+obj-$(CONFIG_HMM) += hmm.o
obj-$(CONFIG_QUICKLIST) += quicklist.o
obj-$(CONFIG_TRANSPARENT_HUGEPAGE) += huge_memory.o khugepaged.o
obj-$(CONFIG_PAGE_COUNTER) += page_counter.o
diff --git a/mm/hmm.c b/mm/hmm.c
new file mode 100644
index 0000000..342b596
--- /dev/null
+++ b/mm/hmm.c
@@ -0,0 +1,86 @@
+/*
+ * Copyright 2013 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * Authors: Jérôme Glisse <jglisse@redhat.com>
+ */
+/*
+ * Refer to include/linux/hmm.h for informations about heterogeneous memory
+ * management or HMM for short.
+ */
+#include <linux/mm.h>
+#include <linux/hmm.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+
+/*
+ * struct hmm - HMM per mm struct
+ *
+ * @mm: mm struct this HMM struct is bound to
+ */
+struct hmm {
+ struct mm_struct *mm;
+};
+
+/*
+ * hmm_register - register HMM against an mm (HMM internal)
+ *
+ * @mm: mm struct to attach to
+ *
+ * This is not intended to be use directly by device driver but by other HMM
+ * component. It allocates an HMM struct if mm does not have one and initialize
+ * it.
+ */
+static struct hmm *hmm_register(struct mm_struct *mm)
+{
+ struct hmm *hmm = NULL;
+
+ if (!mm->hmm) {
+ hmm = kmalloc(sizeof(*hmm), GFP_KERNEL);
+ if (!hmm)
+ return NULL;
+ hmm->mm = mm;
+ }
+
+ spin_lock(&mm->page_table_lock);
+ if (!mm->hmm)
+ /*
+ * The hmm struct can only be free once mm_struct goes away
+ * hence we should always have pre-allocated an new hmm struct
+ * above.
+ */
+ mm->hmm = hmm;
+ else if (hmm)
+ kfree(hmm);
+ hmm = mm->hmm;
+ spin_unlock(&mm->page_table_lock);
+
+ return hmm;
+}
+
+void hmm_mm_destroy(struct mm_struct *mm)
+{
+ struct hmm *hmm;
+
+ /*
+ * We should not need to lock here as no one should be able to register
+ * a new HMM while an mm is being destroy. But just to be safe ...
+ */
+ spin_lock(&mm->page_table_lock);
+ hmm = mm->hmm;
+ mm->hmm = NULL;
+ spin_unlock(&mm->page_table_lock);
+ if (!hmm)
+ return;
+
+ kfree(hmm);
+}
--
2.4.3
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