Messages in this thread | | | Date | Wed, 04 Feb 2009 23:32:00 +0100 | From | Thomas Hellström <> | Subject | Gem GTT mmaps.. |
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Jesse,
I have some concerns about the GEM GTT mmap functionality.
First, a gem object pointer is copied to map->offset and then to the vma->vm_private_data without proper reference counting. This pointer is used in i915_gem_fault() to access the gem object. However if the gem object is destroyed and a process then tries to access data in a vma mapping the (now destroyed) object, it would dereference a stale pointer into kernel space? Shouldn't those pointers be reference counted, and to account for fork(), a vm open and close would be needed to reference count corresponding pointers of newly created and destroyed vmas?
Second, the i915_gem_fault method returns VM_FAULT_SIGBUS if vm_insert_pfn() fails with an -EBUSY. I think that's an error, since that would indicate that the pte was already populated by a racing thread.
/Thomas
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