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The caching mode for buffer objects with VRAM as a possible placement was forced to write-combined, regardless of placement. However, write-combined system memory is expensive to allocate and even though it is pooled, the pool is expensive to shrink, since it involves global CPU TLB flushes. Moreover write-combined system memory from TTM is only reliably available on x86 and DGFX doesn't have an x86 restriction. So regardless of the cpu caching mode selected for a bo, internally use write-back caching mode for system memory on DGFX. Coherency is maintained, but user-space clients may perceive a difference in cpu access speeds. v2: - Update RB- and Ack tags. - Rephrase wording in xe_drm.h (Matt Roper) v3: - Really rephrase wording. Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> Fixes:622f709ca6("drm/xe/uapi: Add support for CPU caching mode") Cc: Pallavi Mishra <pallavi.mishra@intel.com> Cc: Matthew Auld <matthew.auld@intel.com> Cc: dri-devel@lists.freedesktop.org Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Cc: Effie Yu <effie.yu@intel.com> Cc: Matthew Brost <matthew.brost@intel.com> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Jose Souza <jose.souza@intel.com> Cc: Michal Mrozek <michal.mrozek@intel.com> Cc: <stable@vger.kernel.org> # v6.8+ Acked-by: Matthew Auld <matthew.auld@intel.com> Acked-by: José Roberto de Souza <jose.souza@intel.com> Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com> Fixes:622f709ca6("drm/xe/uapi: Add support for CPU caching mode") Acked-by: Michal Mrozek <michal.mrozek@intel.com> Acked-by: Effie Yu <effie.yu@intel.com> #On chat Link: https://patchwork.freedesktop.org/patch/msgid/20240705132828.27714-1-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.