[Intel-gfx] [PATCH] drm/i915: fix i915 running as dom0 under Xen

[Daniel Vetter]

On Thu, Feb 02, 2017 at 10:47:11AM +0100, Juergen Gross wrote:
> Commit 920cf4194954ec ("drm/i915: Introduce an internal allocator for
> disposable private objects") introduced a regression for the kernel
> running as Xen dom0: when switching to graphics mode a GPU HANG
> occurred.
> 
> Reason seems to be a missing adaption similar to that done in
> commit 7453c549f5f648 ("swiotlb: Export swiotlb_max_segment to users")
> to i915_gem_object_get_pages_internal().
> 
> So limit the maximum page order to be used according to the maximum
> swiotlb segment size instead to the complete swiotlb size.
> 
> Signed-off-by: Juergen Gross <jgross at suse.com>
Fixes: 920cf4194954 ("drm/i915: Introduce an internal allocator for disposable private objects")
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
Cc: Daniel Vetter <daniel.vetter at intel.com>
Cc: Jani Nikula <jani.nikula at linux.intel.com>
Cc: intel-gfx at lists.freedesktop.org
Cc: <drm-intel-fixes at lists.freedesktop.org> # v4.10-rc1+

We have a nice script for these :-)
-Daniel

> ---
> Please consider for 4.10 as otherwise 4.10 will be unusable as Xen dom0
> with i915 graphics.
> ---
>  drivers/gpu/drm/i915/i915_gem_internal.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_internal.c b/drivers/gpu/drm/i915/i915_gem_internal.c
> index 4b3ff3e..d09c749 100644
> --- a/drivers/gpu/drm/i915/i915_gem_internal.c
> +++ b/drivers/gpu/drm/i915/i915_gem_internal.c
> @@ -66,8 +66,16 @@ i915_gem_object_get_pages_internal(struct drm_i915_gem_object *obj)
>  
>  	max_order = MAX_ORDER;
>  #ifdef CONFIG_SWIOTLB
> -	if (swiotlb_nr_tbl()) /* minimum max swiotlb size is IO_TLB_SEGSIZE */
> -		max_order = min(max_order, ilog2(IO_TLB_SEGPAGES));
> +	if (swiotlb_nr_tbl()) {
> +		unsigned int max_segment;
> +
> +		max_segment = swiotlb_max_segment();
> +		if (max_segment) {
> +			max_segment = max_t(unsigned int, max_segment,
> +					    PAGE_SIZE) >> PAGE_SHIFT;
> +			max_order = min(max_order, ilog2(max_segment));
> +		}
> +	}
>  #endif
>  
>  	gfp = GFP_KERNEL | __GFP_HIGHMEM | __GFP_RECLAIMABLE;
> -- 
> 2.10.2
> 
> _______________________________________________
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> Intel-gfx at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch