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On TGL, bits 2-4 in the GGTT PTE are not ignored anymore and are instead used for some extra VT-d capabilities. We don't (yet?) have support for those capabilities, but, given that we shared the pte_encode function betweed GGTT and PPGTT, we still set those bits to the PPGTT PPAT values. The DMA engine gets very confused when those bits are set while the iommu is enabled, leading to errors. E.g. when loading the GuC we get: [ 9.796218] DMAR: DRHD: handling fault status reg 2 [ 9.796235] DMAR: [DMA Write] Request device [00:02.0] PASID ffffffff fault addr 0 [fault reason 02] Present bit in context entry is clear [ 9.899215] [drm:intel_guc_fw_upload [i915]] *ERROR* GuC firmware signature verification failed To fix this, just have dedicated gen8_pte_encode function per type of gtt. Also, explicitly set vm->pte_encode for gen8_ppgtt, even if we don't use it, to make sure we don't accidentally assign it to the GGTT one, like we do for gen6_ppgtt, in case we need it in the future. Reported-by: "Sodhi, Vunny" <vunny.sodhi@intel.com> Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com> Cc: Matthew Auld <matthew.auld@intel.com> Cc: Michal Wajdeczko <michal.wajdeczko@intel.com> Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Link: https://patchwork.freedesktop.org/patch/msgid/20200226185657.26445-1-daniele.ceraolospurio@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 Restructured Text 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.