Message-Id: <1521660168-14372-7-git-send-email-rppt@linux.vnet.ibm.com>
Date:   Wed, 21 Mar 2018 21:22:22 +0200
From:   Mike Rapoport <rppt@...ux.vnet.ibm.com>
To:     Jonathan Corbet <corbet@....net>
Cc:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Richard Henderson <rth@...ddle.net>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>,
        Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        James Hogan <jhogan@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        kasan-dev@...glegroups.com, linux-alpha@...r.kernel.org,
        linux-ia64@...r.kernel.org, linux-mips@...ux-mips.org,
        linuxppc-dev@...ts.ozlabs.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, Mike Rapoport <rppt@...ux.vnet.ibm.com>
Subject: [PATCH 06/32] docs/vm: hmm.txt: convert to ReST format

Signed-off-by: Mike Rapoport <rppt@...ux.vnet.ibm.com>
---
 Documentation/vm/hmm.txt | 66 ++++++++++++++++++++----------------------------
 1 file changed, 28 insertions(+), 38 deletions(-)

diff --git a/Documentation/vm/hmm.txt b/Documentation/vm/hmm.txt
index 4d3aac9..3fafa33 100644
--- a/Documentation/vm/hmm.txt
+++ b/Documentation/vm/hmm.txt
@@ -1,4 +1,8 @@
+.. hmm:
+
+=====================================
 Heterogeneous Memory Management (HMM)
+=====================================
 
 Transparently allow any component of a program to use any memory region of said
 program with a device without using device specific memory allocator. This is
@@ -14,19 +18,10 @@ deals with how device memory is represented inside the kernel. Finaly the last
 section present the new migration helper that allow to leverage the device DMA
 engine.
 
+.. contents:: :local:
 
-1) Problems of using device specific memory allocator:
-2) System bus, device memory characteristics
-3) Share address space and migration
-4) Address space mirroring implementation and API
-5) Represent and manage device memory from core kernel point of view
-6) Migrate to and from device memory
-7) Memory cgroup (memcg) and rss accounting
-
-
--------------------------------------------------------------------------------
-
-1) Problems of using device specific memory allocator:
+Problems of using device specific memory allocator
+==================================================
 
 Device with large amount of on board memory (several giga bytes) like GPU have
 historically manage their memory through dedicated driver specific API. This
@@ -68,9 +63,8 @@ only do-able with a share address. It is as well more reasonable to use a share
 address space for all the other patterns.
 
 
--------------------------------------------------------------------------------
-
-2) System bus, device memory characteristics
+System bus, device memory characteristics
+=========================================
 
 System bus cripple share address due to few limitations. Most system bus only
 allow basic memory access from device to main memory, even cache coherency is
@@ -100,9 +94,8 @@ access any memory memory but we must also permit any memory to be migrated to
 device memory while device is using it (blocking CPU access while it happens).
 
 
--------------------------------------------------------------------------------
-
-3) Share address space and migration
+Share address space and migration
+=================================
 
 HMM intends to provide two main features. First one is to share the address
 space by duplication the CPU page table into the device page table so same
@@ -140,14 +133,13 @@ leverage device memory by migrating part of data-set that is actively use by a
 device.
 
 
--------------------------------------------------------------------------------
-
-4) Address space mirroring implementation and API
+Address space mirroring implementation and API
+==============================================
 
 Address space mirroring main objective is to allow to duplicate range of CPU
 page table into a device page table and HMM helps keeping both synchronize. A
 device driver that want to mirror a process address space must start with the
-registration of an hmm_mirror struct:
+registration of an hmm_mirror struct::
 
  int hmm_mirror_register(struct hmm_mirror *mirror,
                          struct mm_struct *mm);
@@ -156,7 +148,7 @@ registration of an hmm_mirror struct:
 
 The locked variant is to be use when the driver is already holding the mmap_sem
 of the mm in write mode. The mirror struct has a set of callback that are use
-to propagate CPU page table:
+to propagate CPU page table::
 
  struct hmm_mirror_ops {
      /* sync_cpu_device_pagetables() - synchronize page tables
@@ -187,7 +179,8 @@ be done with the update.
 
 
 When device driver wants to populate a range of virtual address it can use
-either:
+either::
+
  int hmm_vma_get_pfns(struct vm_area_struct *vma,
                       struct hmm_range *range,
                       unsigned long start,
@@ -211,7 +204,7 @@ that array correspond to an address in the virtual range. HMM provide a set of
 flags to help driver identify special CPU page table entries.
 
 Locking with the update() callback is the most important aspect the driver must
-respect in order to keep things properly synchronize. The usage pattern is :
+respect in order to keep things properly synchronize. The usage pattern is::
 
  int driver_populate_range(...)
  {
@@ -251,9 +244,8 @@ concurrently for multiple devices. Waiting for each device to report commands
 as executed is serialize (there is no point in doing this concurrently).
 
 
--------------------------------------------------------------------------------
-
-5) Represent and manage device memory from core kernel point of view
+Represent and manage device memory from core kernel point of view
+=================================================================
 
 Several differents design were try to support device memory. First one use
 device specific data structure to keep information about migrated memory and
@@ -269,14 +261,14 @@ un-aware of the difference. We only need to make sure that no one ever try to
 map those page from the CPU side.
 
 HMM provide a set of helpers to register and hotplug device memory as a new
-region needing struct page. This is offer through a very simple API:
+region needing struct page. This is offer through a very simple API::
 
  struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops,
                                    struct device *device,
                                    unsigned long size);
  void hmm_devmem_remove(struct hmm_devmem *devmem);
 
-The hmm_devmem_ops is where most of the important things are:
+The hmm_devmem_ops is where most of the important things are::
 
  struct hmm_devmem_ops {
      void (*free)(struct hmm_devmem *devmem, struct page *page);
@@ -294,13 +286,12 @@ second callback happens whenever CPU try to access a device page which it can
 not do. This second callback must trigger a migration back to system memory.
 
 
--------------------------------------------------------------------------------
-
-6) Migrate to and from device memory
+Migrate to and from device memory
+=================================
 
 Because CPU can not access device memory, migration must use device DMA engine
 to perform copy from and to device memory. For this we need a new migration
-helper:
+helper::
 
  int migrate_vma(const struct migrate_vma_ops *ops,
                  struct vm_area_struct *vma,
@@ -319,7 +310,7 @@ such migration base on range of address the device is actively accessing.
 
 The migrate_vma_ops struct define two callbacks. First one (alloc_and_copy())
 control destination memory allocation and copy operation. Second one is there
-to allow device driver to perform cleanup operation after migration.
+to allow device driver to perform cleanup operation after migration::
 
  struct migrate_vma_ops {
      void (*alloc_and_copy)(struct vm_area_struct *vma,
@@ -353,9 +344,8 @@ bandwidth but this is considered as a rare event and a price that we are
 willing to pay to keep all the code simpler.
 
 
--------------------------------------------------------------------------------
-
-7) Memory cgroup (memcg) and rss accounting
+Memory cgroup (memcg) and rss accounting
+========================================
 
 For now device memory is accounted as any regular page in rss counters (either
 anonymous if device page is use for anonymous, file if device page is use for
-- 
2.7.4

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