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When running under virtualization (vGPU active), we must disable the lazy PPGTT page table initialization optimization introduced by commit1482667324("drm/i915: Only initialize partially filled pagetables"). We must do this because GVT-g makes unduly assumptions about guest behaviour, which this optimization breaks. This results in following looking errors in the host: ERROR gvt: guest page write error -22, gfn 0x7ada8, pa 0x7ada89a8, var 0x6, len 1 The real fix is to not to depend on i915 driver behaviour, but instead either rely on only the contracts that i915 has with the hardware, or add some paravirtualization. While the real fix is en route, it won't be finished in time for 4.15, so the best option is to disable the optimization for now when vGPU is active to avoid breaking 4.15 guests in existing VM environments. Fixes:1482667324("drm/i915: Only initialize partially filled pagetables") Suggested-by: Xiaolin Zhang <xiaolin.zhang@intel.com> Signed-off-by: Xiaolin Zhang <xiaolin.zhang@intel.com> [Joonas: Rewrote the commit message and added tags.] Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Cc: Zhenyu Wang <zhenyuw@linux.intel.com> Cc: Zhi Wang <zhi.a.wang@intel.com> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Matthew Auld <matthew.auld@intel.com> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> Cc: Jani Nikula <jani.nikula@linux.intel.com> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com> Acked-by: Chris Wilson <chris@chris-wilson.co.uk> Acked-by: Zhenyu Wang <zhenyuw@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20171023153209.10527-1-joonas.lahtinen@linux.intel.com (cherry picked from commit22a8a4fc93) Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.