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Replace GEM VRAM with GEM SHMEM in bochs. The new memory manager stores buffer objects in system memory. Makes the driver's memory management more reliably. Most of the changes are hidden in external helpers that allocate buffers. Replacing DRM_GEM_VRAM_DRIVER with DRM_GEM_SHMEM_DRIVER_OPS swaps these. With GEM VRAM, the video memory was updated directly by the DRM client. The biggest change within bochs is in atomic_update, which now updates video memory via memcpy() from the BO in system memory. Shadow-plane helpers maintaining the pointers to the buffer's data, so bochs doesn't have to. The update is triggered by each page flip's call to the framebuffer's dirty helper. The driver supports damage clipping to minimize memcpy() overhead. The advantage of GEM SHMEM is that it makes memory management more reliable. Given DRM's double buffering during page flips, the minimum amount of video memory is three times the maximum consumption in some pathological cases. For example, if the maximum size of a GEM buffer is 1920x1080-32 (i.e., 32-bit FullHD), the buffer size is 8 MiB. Display hardware has to provide at lease 24 MiB to reliably page flip such configurations. This cannot always be guaranteed and bochs already contains code to rule out <4 MiB configurations. With GEM SHMEM, only 8 MiB of video memory are required for the given example. Unsupported modes can be sorted out easily. Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Acked-by: Gerd Hoffmann <kraxel@redhat.com> Link: https://patchwork.freedesktop.org/patch/msgid/20240902105546.792625-9-tzimmermann@suse.de
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.