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RDMA NICs typically requires the VRAM dma-bufs to be pinned in VRAM for pcie-p2p communication, since they don't fully support the move_notify() scheme. We would like to support that. However allowing unaccounted pinning of VRAM creates a DOS vector so up until now we haven't allowed it. However with cgroups support in TTM, the amount of VRAM allocated to a cgroup can be limited, and since also the pinned memory is accounted as allocated VRAM we should be safe. An analogy with system memory can be made if we observe the similarity with kernel system memory that is allocated as the result of user-space action and that is accounted using __GFP_ACCOUNT. Ideally, to be more flexible, we would add a "pinned_memory", or possibly "kernel_memory" limit to the dmem cgroups controller, that would additionally limit the memory that is pinned in this way. If we let that limit default to the dmem::max limit we can introduce that without needing to care about regressions. Considering that we already pin VRAM in this way for at least page-table memory and LRC memory, and the above path to greater flexibility, allow this also for dma-bufs. v2: - Update comments about pinning in the dma-buf kunit test (Niranjana Vishwanathapura) Cc: Dave Airlie <airlied@gmail.com> Cc: Simona Vetter <simona.vetter@ffwll.ch> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Cc: Maarten Lankhorst <maarten.lankhorst@intel.com> Cc: Matthew Brost <matthew.brost@intel.com> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com> Cc: Lucas De Marchi <lucas.demarchi@intel.com> Cc: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> Acked-by: Simona Vetter <simona.vetter@ffwll.ch> Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Link: https://lore.kernel.org/r/20250918092207.54472-4-thomas.hellstrom@linux.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.