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由 Jon Bloomfield 提交于
BXT has a H/W issue with IOMMU which can lead to system hangs when Aperture accesses are queued within the GAM behind GTT Accesses. This patch avoids the condition by wrapping all GTT updates in stop_machine and using a flushing read prior to restarting the machine. The stop_machine guarantees no new Aperture accesses can begin while the PTE writes are being emmitted. The flushing read ensures that any following Aperture accesses cannot begin until the PTE writes have been cleared out of the GAM's fifo. Only FOLLOWING Aperture accesses need to be separated from in flight PTE updates. PTE Writes may follow tightly behind already in flight Aperture accesses, so no flushing read is required at the start of a PTE update sequence. This issue was reproduced by running igt/gem_readwrite and igt/gem_render_copy simultaneously from different processes, each in a tight loop, with INTEL_IOMMU enabled. This patch was originally published as: drm/i915: Serialize GTT Updates on BXT v2: Move bxt/iommu detection into static function Remove #ifdef CONFIG_INTEL_IOMMU protection Make function names more reflective of purpose Move flushing read into static function v3: Tidy up for checkpatch.pl Testcase: igt/gem_concurrent_blit Signed-off-by: NJon Bloomfield <jon.bloomfield@intel.com> Cc: John Harrison <john.C.Harrison@intel.com> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Daniel Vetter <daniel.vetter@intel.com> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/1495641251-30022-1-git-send-email-jon.bloomfield@intel.comReviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com> Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
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