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Avoid multiple CPU page faults to the same device page racing by trying to lock the page in do_swap_page before taking an extra reference to the page. This prevents scenarios where multiple CPU page faults each take an extra reference to a device page, which could abort migration in folio_migrate_mapping. With the device page being locked in do_swap_page, the migrate_vma_* functions need to be updated to avoid locking the fault_page argument. Prior to this change, a livelock scenario could occur in Xe's (Intel GPU DRM driver) SVM implementation if enough threads faulted the same device page. v3: - Put page after unlocking page (Alistair) - Warn on spliting a TPH which is fault page (Alistair) - Warn on dst page == fault page (Alistair) v6: - Add more verbose comment around THP (Alistair) v7: - Fix migrate_device_finalize alignment (Checkpatch) Cc: Alistair Popple <apopple@nvidia.com> Cc: Philip Yang <Philip.Yang@amd.com> Cc: Felix Kuehling <felix.kuehling@amd.com> Cc: Christian König <christian.koenig@amd.com> Cc: Andrew Morton <akpm@linux-foundation.org> Suggested-by: Simona Vetter <simona.vetter@ffwll.ch> Signed-off-by: Matthew Brost <matthew.brost@intel.com> Reviewed-by: Alistair Popple <apopple@nvidia.com> Tested-by: Alistair Popple <apopple@nvidia.com> Link: https://patchwork.freedesktop.org/patch/msgid/20250306012657.3505757-4-matthew.brost@intel.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.