[Intel-gfx] [PATCH v4] drm/i915: Avoid writing relocs with addresses in non-canonical form

[Chris Wilson]

On Fri, Dec 18, 2015 at 09:01:03PM +0100, Michał Winiarski wrote:
> According to bspec, some parts of HW require the addresses to be in
> a canonical form, where bits [63:48] == [47]. Let's convert addresses to
> canonical form prior to relocating and return converted offsets to
> userspace. We also need to make sure that userspace is using addresses
> in canonical form in case of softpin.
> 
> v2: Whitespace fixup, gen8_canonical_addr description (Chris, Ville)
> v3: Rebase on top of softpin, fix a hole in relocate_entry,
>     s/expect/require (Chris)
> v4: Handle softpin in validate_exec_list (Chris)
> 
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Michel Thierry <michel.thierry at intel.com>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Signed-off-by: Michał Winiarski <michal.winiarski at intel.com>

> @@ -625,8 +645,9 @@ i915_gem_execbuffer_reserve_vma(struct i915_vma *vma,
>  			entry->flags |= __EXEC_OBJECT_HAS_FENCE;
>  	}
>  
> -	if (entry->offset != vma->node.start) {
> -		entry->offset = vma->node.start;
> +	offset = gen8_canonical_addr(vma->node.start);
> +	if (entry->offset != offset) {

entry->offset is now in normal form.

> +		entry->offset = offset;
>  		*need_reloc = true;
>  	}

But we need to convert back to canonical form again on the userspace
boundary (copy_to_user).
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre