diff --git a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
index bc95210788073..7ab9e98bcbd21 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_stolen.c
@@ -913,7 +913,7 @@ i915_gem_stolen_lmem_setup(struct drm_i915_private *i915, u16 type,
 		dsm_base = intel_uncore_read64(uncore, GEN12_DSMBASE) & GEN12_BDSM_MASK;
 		if (WARN_ON(lmem_size < dsm_base))
 			return ERR_PTR(-ENODEV);
-		dsm_size = lmem_size - dsm_base;
+		dsm_size = ALIGN_DOWN(lmem_size - dsm_base, SZ_1M);
 	}
 
 	io_size = dsm_size;