drm/i915: stop using kmap in i915_gem_object_map

kmap for !PageHighmem is just a convoluted way to say page_address, and
kunmap is a no-op in that case.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Link: https://lkml.kernel.org/r/20201002122204.1534411-8-hch@lst.deSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/gpu/drm/i915/gem/i915_gem_pages.c

@@ -162,8 +162,6 @@ static void unmap_object(struct drm_i915_gem_object *obj, void *ptr)
 {
 	if (is_vmalloc_addr(ptr))
 		vunmap(ptr);
-	else
-		kunmap(kmap_to_page(ptr));
 }
 
 struct sg_table *
@@ -277,11 +275,10 @@ static void *i915_gem_object_map(struct drm_i915_gem_object *obj,
 		 * forever.
 		 *
 		 * So if the page is beyond the 32b boundary, make an explicit
-		 * vmap. On 64b, this check will be optimised away as we can
-		 * directly kmap any page on the system.
+		 * vmap.
 		 */
 		if (!PageHighMem(page))
-			return kmap(page);
+			return page_address(page);
 	}
 
 	mem = stack;