mm/hmm: heterogeneous memory management (HMM for short)

HMM provides 3 separate types of 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.

Link: http://lkml.kernel.org/r/20170817000548.32038-3-jglisse@redhat.com
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Signed-off-by: Evgeny Baskakov <ebaskakov@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>
Cc: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Nellans <dnellans@nvidia.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Bob Liu <liubo95@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Jérôme Glisse 2017-09-08 16:11:23 -07:00 committed by Linus Torvalds
parent bffc33ec53
commit 133ff0eac9
6 changed files with 249 additions and 1 deletions

152
include/linux/hmm.h Normal file
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@ -0,0 +1,152 @@
/*
* 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: ©´me Glisse <jglisse@redhat.com>
*/
/*
* Heterogeneous Memory Management (HMM)
*
* See Documentation/vm/hmm.txt for reasons and overview of what HMM is and it
* is for. Here we focus on the HMM API description, with some explanation of
* the underlying implementation.
*
* Short description: HMM provides a set of helpers to share a virtual address
* space between CPU and a device, so that the device can access any valid
* address of the process (while still obeying memory protection). HMM also
* provides helpers to migrate process memory to device memory, and back. Each
* set of functionality (address space mirroring, and migration to and from
* device memory) can be used independently of the other.
*
*
* HMM address space mirroring API:
*
* Use HMM address space mirroring if you want to mirror range of the CPU page
* table of a process into a device page table. Here, "mirror" means "keep
* synchronized". Prerequisites: the device must provide the ability to write-
* protect its page tables (at PAGE_SIZE granularity), and must be able to
* recover from the resulting potential page faults.
*
* HMM guarantees that at any point in time, a given virtual address points to
* either the same memory in both CPU and device page tables (that is: CPU and
* device page tables each point to the same pages), or that one page table (CPU
* or device) points to no entry, while the other still points to the old page
* for the address. The latter case happens when the CPU page table update
* happens first, and then the update is mirrored over to the device page table.
* This does not cause any issue, because the CPU page table cannot start
* pointing to a new page until the device page table is invalidated.
*
* HMM uses mmu_notifiers to monitor the CPU page tables, and forwards any
* updates to each device driver that has registered a mirror. It also provides
* some API calls to help with taking a snapshot of the CPU page table, and to
* synchronize with any updates that might happen concurrently.
*
*
* HMM migration to and from device memory:
*
* HMM provides a set of helpers to hotplug device memory as ZONE_DEVICE, with
* a new MEMORY_DEVICE_PRIVATE type. This provides a struct page for each page
* of the device memory, and allows the device driver to manage its memory
* using those struct pages. Having struct pages for device memory makes
* migration easier. Because that memory is not addressable by the CPU it must
* never be pinned to the device; in other words, any CPU page fault can always
* cause the device memory to be migrated (copied/moved) back to regular memory.
*
* A new migrate helper (migrate_vma()) has been added (see mm/migrate.c) that
* allows use of a device DMA engine to perform the copy operation between
* regular system memory and device memory.
*/
#ifndef LINUX_HMM_H
#define LINUX_HMM_H
#include <linux/kconfig.h>
#if IS_ENABLED(CONFIG_HMM)
/*
* hmm_pfn_t - HMM uses its own pfn type to keep several flags per page
*
* Flags:
* HMM_PFN_VALID: pfn is valid
* HMM_PFN_WRITE: CPU page table has 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
/*
* hmm_pfn_t_to_page() - return struct page pointed to by a valid hmm_pfn_t
* @pfn: hmm_pfn_t to convert to struct page
* Returns: struct page pointer if pfn is a valid hmm_pfn_t, NULL otherwise
*
* If the hmm_pfn_t is valid (ie valid flag set) then return the struct page
* matching the pfn value stored in the hmm_pfn_t. Otherwise return NULL.
*/
static inline struct page *hmm_pfn_t_to_page(hmm_pfn_t pfn)
{
if (!(pfn & HMM_PFN_VALID))
return NULL;
return pfn_to_page(pfn >> HMM_PFN_SHIFT);
}
/*
* hmm_pfn_t_to_pfn() - return pfn value store in a hmm_pfn_t
* @pfn: hmm_pfn_t to extract pfn from
* Returns: pfn value if hmm_pfn_t is valid, -1UL otherwise
*/
static inline unsigned long hmm_pfn_t_to_pfn(hmm_pfn_t pfn)
{
if (!(pfn & HMM_PFN_VALID))
return -1UL;
return (pfn >> HMM_PFN_SHIFT);
}
/*
* hmm_pfn_t_from_page() - create a valid hmm_pfn_t value from struct page
* @page: struct page pointer for which to create the hmm_pfn_t
* Returns: valid hmm_pfn_t for the page
*/
static inline hmm_pfn_t hmm_pfn_t_from_page(struct page *page)
{
return (page_to_pfn(page) << HMM_PFN_SHIFT) | HMM_PFN_VALID;
}
/*
* hmm_pfn_t_from_pfn() - create a valid hmm_pfn_t value from pfn
* @pfn: pfn value for which to create the hmm_pfn_t
* Returns: valid hmm_pfn_t for the pfn
*/
static inline hmm_pfn_t hmm_pfn_t_from_pfn(unsigned long pfn)
{
return (pfn << HMM_PFN_SHIFT) | HMM_PFN_VALID;
}
/* Below are for HMM internal use only! Not to be used by device driver! */
void hmm_mm_destroy(struct mm_struct *mm);
static inline void hmm_mm_init(struct mm_struct *mm)
{
mm->hmm = NULL;
}
#else /* IS_ENABLED(CONFIG_HMM) */
/* Below are for HMM internal use only! Not to be used by device driver! */
static inline void hmm_mm_destroy(struct mm_struct *mm) {}
static inline void hmm_mm_init(struct mm_struct *mm) {}
#endif /* IS_ENABLED(CONFIG_HMM) */
#endif /* LINUX_HMM_H */

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@ -23,6 +23,7 @@
struct address_space;
struct mem_cgroup;
struct hmm;
/*
* Each physical page in the system has a struct page associated with
@ -503,6 +504,11 @@ struct mm_struct {
atomic_long_t hugetlb_usage;
#endif
struct work_struct async_put_work;
#if IS_ENABLED(CONFIG_HMM)
/* HMM needs to track a few things per mm */
struct hmm *hmm;
#endif
} __randomize_layout;
extern struct mm_struct init_mm;

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@ -37,6 +37,7 @@
#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>
@ -824,6 +825,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
mm_init_owner(mm, p);
RCU_INIT_POINTER(mm->exe_file, NULL);
mmu_notifier_mm_init(mm);
hmm_mm_init(mm);
init_tlb_flush_pending(mm);
#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
mm->pmd_huge_pte = NULL;
@ -903,6 +905,7 @@ 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);
put_user_ns(mm->user_ns);

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@ -692,6 +692,19 @@ config ZONE_DEVICE
If FS_DAX is enabled, then say Y.
config ARCH_HAS_HMM
bool
default y
depends on (X86_64 || PPC64)
depends on ZONE_DEVICE
depends on MMU && 64BIT
depends on MEMORY_HOTPLUG
depends on MEMORY_HOTREMOVE
depends on SPARSEMEM_VMEMMAP
config HMM
bool
config FRAME_VECTOR
bool

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@ -39,7 +39,7 @@ obj-y := filemap.o mempool.o oom_kill.o \
mm_init.o mmu_context.o percpu.o slab_common.o \
compaction.o vmacache.o swap_slots.o \
interval_tree.o list_lru.o workingset.o \
debug.o $(mmu-y)
debug.o hmm.o $(mmu-y)
obj-y += init-mm.o

74
mm/hmm.c Normal file
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@ -0,0 +1,74 @@
/*
* 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: ©´me Glisse <jglisse@redhat.com>
*/
/*
* Refer to include/linux/hmm.h for information about heterogeneous memory
* management or HMM for short.
*/
#include <linux/mm.h>
#include <linux/hmm.h>
#include <linux/slab.h>
#include <linux/sched.h>
#ifdef CONFIG_HMM
/*
* 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 used directly by device drivers. It allocates an
* HMM struct if mm does not have one, and initializes it.
*/
static struct hmm *hmm_register(struct mm_struct *mm)
{
if (!mm->hmm) {
struct hmm *hmm = NULL;
hmm = kmalloc(sizeof(*hmm), GFP_KERNEL);
if (!hmm)
return NULL;
hmm->mm = mm;
spin_lock(&mm->page_table_lock);
if (!mm->hmm)
mm->hmm = hmm;
else
kfree(hmm);
spin_unlock(&mm->page_table_lock);
}
/*
* The hmm struct can only be freed once the mm_struct goes away,
* hence we should always have pre-allocated an new hmm struct
* above.
*/
return mm->hmm;
}
void hmm_mm_destroy(struct mm_struct *mm)
{
kfree(mm->hmm);
}
#endif /* CONFIG_HMM */