On Mon, Nov 02, 2020 at 10:23:20AM +0100, David Hildenbrand wrote:

quoted

  int __init kernel_map_pages_in_pgd(pgd_t *pgd, u64 pfn, unsigned long address,
  				   unsigned numpages, unsigned long page_flags)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 14e397f3752c..ab0ef6bd351d 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h

@@ -2924,7 +2924,11 @@ static inline bool debug_pagealloc_enabled_static(void)
  	return static_branch_unlikely(&_debug_pagealloc_enabled);
  }
-#if defined(CONFIG_DEBUG_PAGEALLOC) || defined(CONFIG_ARCH_HAS_SET_DIRECT_MAP)
+#ifdef CONFIG_DEBUG_PAGEALLOC
+/*
+ * To support DEBUG_PAGEALLOC architecture must ensure that
+ * __kernel_map_pages() never fails

Maybe add here, that this implies mapping everything via PTEs during boot.

This is more of an implementation detail, while assumption that
__kernel_map_pages() does not fail is somewhat a requirement :)

Acked-by: David Hildenbrand <redacted>

Thanks!

-- 
Thanks,

David / dhildenb

-- 
Sincerely yours,
Mike.