linux/arch
Alistair Popple af5cdaf822 mm: remove special swap entry functions
Patch series "Add support for SVM atomics in Nouveau", v11.

Introduction
============

Some devices have features such as atomic PTE bits that can be used to
implement atomic access to system memory.  To support atomic operations to
a shared virtual memory page such a device needs access to that page which
is exclusive of the CPU.  This series introduces a mechanism to
temporarily unmap pages granting exclusive access to a device.

These changes are required to support OpenCL atomic operations in Nouveau
to shared virtual memory (SVM) regions allocated with the
CL_MEM_SVM_ATOMICS clSVMAlloc flag.  A more complete description of the
OpenCL SVM feature is available at
https://www.khronos.org/registry/OpenCL/specs/3.0-unified/html/
OpenCL_API.html#_shared_virtual_memory .

Implementation
==============

Exclusive device access is implemented by adding a new swap entry type
(SWAP_DEVICE_EXCLUSIVE) which is similar to a migration entry.  The main
difference is that on fault the original entry is immediately restored by
the fault handler instead of waiting.

Restoring the entry triggers calls to MMU notifers which allows a device
driver to revoke the atomic access permission from the GPU prior to the
CPU finalising the entry.

Patches
=======

Patches 1 & 2 refactor existing migration and device private entry
functions.

Patches 3 & 4 rework try_to_unmap_one() by splitting out unrelated
functionality into separate functions - try_to_migrate_one() and
try_to_munlock_one().

Patch 5 renames some existing code but does not introduce functionality.

Patch 6 is a small clean-up to swap entry handling in copy_pte_range().

Patch 7 contains the bulk of the implementation for device exclusive
memory.

Patch 8 contains some additions to the HMM selftests to ensure everything
works as expected.

Patch 9 is a cleanup for the Nouveau SVM implementation.

Patch 10 contains the implementation of atomic access for the Nouveau
driver.

Testing
=======

This has been tested with upstream Mesa 21.1.0 and a simple OpenCL program
which checks that GPU atomic accesses to system memory are atomic.
Without this series the test fails as there is no way of write-protecting
the page mapping which results in the device clobbering CPU writes.  For
reference the test is available at
https://ozlabs.org/~apopple/opencl_svm_atomics/

Further testing has been performed by adding support for testing exclusive
access to the hmm-tests kselftests.

This patch (of 10):

Remove multiple similar inline functions for dealing with different types
of special swap entries.

Both migration and device private swap entries use the swap offset to
store a pfn.  Instead of multiple inline functions to obtain a struct page
for each swap entry type use a common function pfn_swap_entry_to_page().
Also open-code the various entry_to_pfn() functions as this results is
shorter code that is easier to understand.

Link: https://lkml.kernel.org/r/20210616105937.23201-1-apopple@nvidia.com
Link: https://lkml.kernel.org/r/20210616105937.23201-2-apopple@nvidia.com
Signed-off-by: Alistair Popple <apopple@nvidia.com>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-07-01 11:06:03 -07:00
..
alpha mm/thp: define default pmd_pgtable() 2021-07-01 11:06:03 -07:00
arc mm/thp: define default pmd_pgtable() 2021-07-01 11:06:03 -07:00
arm mm/thp: define default pmd_pgtable() 2021-07-01 11:06:03 -07:00
arm64 mm/thp: define default pmd_pgtable() 2021-07-01 11:06:03 -07:00
csky mm/thp: define default pmd_pgtable() 2021-07-01 11:06:03 -07:00
h8300 h8300: remove unused variable 2021-06-29 10:53:52 -07:00
hexagon mm/thp: define default pmd_pgtable() 2021-07-01 11:06:03 -07:00
ia64 mm/thp: define default pmd_pgtable() 2021-07-01 11:06:03 -07:00
m68k mm/thp: define default pmd_pgtable() 2021-07-01 11:06:03 -07:00
microblaze mm/thp: define default pmd_pgtable() 2021-07-01 11:06:03 -07:00
mips mm/thp: define default pmd_pgtable() 2021-07-01 11:06:03 -07:00
nds32 mm/thp: define default pmd_pgtable() 2021-07-01 11:06:03 -07:00
nios2 mm/thp: define default pmd_pgtable() 2021-07-01 11:06:03 -07:00
openrisc mm/thp: define default pmd_pgtable() 2021-07-01 11:06:03 -07:00
parisc mm/thp: define default pmd_pgtable() 2021-07-01 11:06:03 -07:00
powerpc mm/thp: define default pmd_pgtable() 2021-07-01 11:06:03 -07:00
riscv mm/thp: define default pmd_pgtable() 2021-07-01 11:06:03 -07:00
s390 mm: remove special swap entry functions 2021-07-01 11:06:03 -07:00
sh mm/thp: define default pmd_pgtable() 2021-07-01 11:06:03 -07:00
sparc mm/thp: define default pmd_pgtable() 2021-07-01 11:06:03 -07:00
um mm/thp: define default pmd_pgtable() 2021-07-01 11:06:03 -07:00
x86 mm/thp: define default pmd_pgtable() 2021-07-01 11:06:03 -07:00
xtensa mm/thp: define default pmd_pgtable() 2021-07-01 11:06:03 -07:00
.gitignore .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
Kconfig Add Landlock, a new LSM from Mickaël Salaün <mic@linux.microsoft.com> 2021-05-01 18:50:44 -07:00