> Running the updated xf86-video-intel driver uncovered a bug in the
> kernel drm code. The page fault handler wasn't handling some of the
> possible errors correctly. This made the X server die with a SIGSEGV.
> The diff below brings things closer to what Linux does, and seems to
> fix the crashes I was seeing. A bit more testing would be welcome
> though. Note that this needs the commit to drmP.h I just made, which
> might not have made it to all the anoncvs servers yet.
>
>
> Index: i915_gem.c
> ===================================================================
> RCS file: /cvs/src/sys/dev/pci/drm/i915/i915_gem.c,v
> retrieving revision 1.68
> diff -u -p -r1.68 i915_gem.c
> --- i915_gem.c 2 Feb 2014 10:54:10 -0000 1.68
> +++ i915_gem.c 4 Feb 2014 22:47:53 -0000
> @@ -1522,6 +1522,7 @@ i915_gem_fault(struct drm_gem_object *ge
> NULL, NULL);
> DRM_UNLOCK();
> dev_priv->entries--;
> + pmap_update(ufi->orig_map->pmap);
> uvm_wait("intelflt");
> return (VM_PAGER_REFAULT);
> }
> @@ -1533,18 +1534,42 @@ unlock:
> DRM_UNLOCK();
> dev_priv->entries--;
> pmap_update(ufi->orig_map->pmap);
> - if (ret == -EIO) {
> +
> + switch (ret) {
> + case -EIO:
> + /* If this -EIO is due to a gpu hang, give the reset code a
> + * chance to clean up the mess. Otherwise return the proper
> + * SIGBUS. */
> + if (!atomic_read(&dev_priv->mm.wedged))
> + return VM_PAGER_ERROR;
> + case -EAGAIN:
> + /* Give the error handler a chance to run and move the
> + * objects off the GPU active list. Next time we service the
> + * fault, we should be able to transition the page into the
> + * GTT without touching the GPU (and so avoid further
> + * EIO/EGAIN). If the GPU is wedged, then there is no issue
> + * with coherency, just lost writes.
> + */
> +#if 0
> + set_need_resched();
> +#endif
> + case 0:
> + case -ERESTART:
> + case -EINTR:
> + case -EBUSY:
> /*
> - * EIO means we're wedged, so upon resetting the gpu we'll
> - * be alright and can refault. XXX only on resettable chips.
> + * EBUSY is ok: this just means that another thread
> + * already did the job.
> */
> - ret = VM_PAGER_REFAULT;
> - } else if (ret) {
> - ret = VM_PAGER_ERROR;
> - } else {
> - ret = VM_PAGER_OK;
> + return VM_PAGER_OK;
> + case -ENOMEM:
> + return VM_PAGER_ERROR;
> + case -ENOSPC:
> + return VM_PAGER_ERROR;
> + default:
> + WARN_ONCE(ret, "unhandled error in i915_gem_fault: %i\n", ret);
> + return VM_PAGER_ERROR;
> }
> - return ret;
> }
>
> /**
>
Thanks, this works good for me too -- no X segfaults anymore.
