On Mon, Nov 02, 2020 at 10:19:36AM +0100, David Hildenbrand wrote:

On 01.11.20 18:08, Mike Rapoport wrote:

quoted

From: Mike Rapoport <redacted>

When DEBUG_PAGEALLOC or ARCH_HAS_SET_DIRECT_MAP is enabled a page may be
not present in the direct map and has to be explicitly mapped before it
could be copied.

Introduce hibernate_map_page() that will explicitly use
set_direct_map_{default,invalid}_noflush() for ARCH_HAS_SET_DIRECT_MAP case
and debug_pagealloc_map_pages() for DEBUG_PAGEALLOC case.

The remapping of the pages in safe_copy_page() presumes that it only
changes protection bits in an existing PTE and so it is safe to ignore
return value of set_direct_map_{default,invalid}_noflush().

Still, add a WARN_ON() so that future changes in set_memory APIs will not
silently break hibernation.

Signed-off-by: Mike Rapoport <redacted>
Acked-by: Rafael J. Wysocki <redacted>
---
  include/linux/mm.h      | 12 ------------
  kernel/power/snapshot.c | 30 ++++++++++++++++++++++++++++--
  2 files changed, 28 insertions(+), 14 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 1fc0609056dc..14e397f3752c 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h

@@ -2927,16 +2927,6 @@ static inline bool debug_pagealloc_enabled_static(void)
  #if defined(CONFIG_DEBUG_PAGEALLOC) || defined(CONFIG_ARCH_HAS_SET_DIRECT_MAP)
  extern void __kernel_map_pages(struct page *page, int numpages, int enable);
-/*
- * When called in DEBUG_PAGEALLOC context, the call should most likely be
- * guarded by debug_pagealloc_enabled() or debug_pagealloc_enabled_static()
- */
-static inline void
-kernel_map_pages(struct page *page, int numpages, int enable)
-{
-	__kernel_map_pages(page, numpages, enable);
-}
-
  static inline void debug_pagealloc_map_pages(struct page *page,
  					     int numpages, int enable)
  {

@@ -2948,8 +2938,6 @@ static inline void debug_pagealloc_map_pages(struct page *page,
  extern bool kernel_page_present(struct page *page);
  #endif	/* CONFIG_HIBERNATION */
  #else	/* CONFIG_DEBUG_PAGEALLOC || CONFIG_ARCH_HAS_SET_DIRECT_MAP */
-static inline void
-kernel_map_pages(struct page *page, int numpages, int enable) {}
  static inline void debug_pagealloc_map_pages(struct page *page,
  					     int numpages, int enable) {}
  #ifdef CONFIG_HIBERNATION

diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index 46b1804c1ddf..054c8cce4236 100644
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c

@@ -76,6 +76,32 @@ static inline void hibernate_restore_protect_page(void *page_address) {}
  static inline void hibernate_restore_unprotect_page(void *page_address) {}
  #endif /* CONFIG_STRICT_KERNEL_RWX  && CONFIG_ARCH_HAS_SET_MEMORY */
+static inline void hibernate_map_page(struct page *page, int enable)
+{
+	if (IS_ENABLED(CONFIG_ARCH_HAS_SET_DIRECT_MAP)) {
+		unsigned long addr = (unsigned long)page_address(page);
+		int ret;
+
+		/*
+		 * This should not fail because remapping a page here means
+		 * that we only update protection bits in an existing PTE.
+		 * It is still worth to have WARN_ON() here if something
+		 * changes and this will no longer be the case.
+		 */
+		if (enable)
+			ret = set_direct_map_default_noflush(page);
+		else
+			ret = set_direct_map_invalid_noflush(page);
+
+		if (WARN_ON(ret))
+			return;

People seem to prefer pr_warn() now that production kernels have panic on
warn enabled. It's weird.

Weird indeed as the whole point of WARN to yell without causing a
crash...
I can change to pr_warn though...

quoted

+
+		flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
+	} else {
+		debug_pagealloc_map_pages(page, 1, enable);

Reviewed-by: David Hildenbrand <redacted>

Thanks!

-- 
Thanks,

David / dhildenb

-- 
Sincerely yours,
Mike.

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