x86/mm/64: define ARCH_PAGE_TABLE_SYNC_MASK and arch_sync_kernel_mappings()

Define ARCH_PAGE_TABLE_SYNC_MASK and arch_sync_kernel_mappings() to ensure
page tables are properly synchronized when calling p*d_populate_kernel().

For 5-level paging, synchronization is performed via
pgd_populate_kernel().  In 4-level paging, pgd_populate() is a no-op, so
synchronization is instead performed at the P4D level via
p4d_populate_kernel().

This fixes intermittent boot failures on systems using 4-level paging and
a large amount of persistent memory:

  BUG: unable to handle page fault for address: ffffe70000000034
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  RIP: 0010:__init_single_page+0x9/0x6d
  Call Trace:
   <TASK>
   __init_zone_device_page+0x17/0x5d
   memmap_init_zone_device+0x154/0x1bb
   pagemap_range+0x2e0/0x40f
   memremap_pages+0x10b/0x2f0
   devm_memremap_pages+0x1e/0x60
   dev_dax_probe+0xce/0x2ec [device_dax]
   dax_bus_probe+0x6d/0xc9
   [... snip ...]
   </TASK>

It also fixes a crash in vmemmap_set_pmd() caused by accessing vmemmap
before sync_global_pgds() [1]:

  BUG: unable to handle page fault for address: ffffeb3ff1200000
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: Oops: 0002 [#1] PREEMPT SMP NOPTI
  Tainted: [W]=WARN
  RIP: 0010:vmemmap_set_pmd+0xff/0x230
   <TASK>
   vmemmap_populate_hugepages+0x176/0x180
   vmemmap_populate+0x34/0x80
   __populate_section_memmap+0x41/0x90
   sparse_add_section+0x121/0x3e0
   __add_pages+0xba/0x150
   add_pages+0x1d/0x70
   memremap_pages+0x3dc/0x810
   devm_memremap_pages+0x1c/0x60
   xe_devm_add+0x8b/0x100 [xe]
   xe_tile_init_noalloc+0x6a/0x70 [xe]
   xe_device_probe+0x48c/0x740 [xe]
   [... snip ...]

Link: https://lkml.kernel.org/r/[email protected]
Fixes: 8d40091 ("x86/vmemmap: handle unpopulated sub-pmd ranges")
Signed-off-by: Harry Yoo <[email protected]>
Closes: https://lore.kernel.org/linux-mm/[email protected] [1]
Suggested-by: Dave Hansen <[email protected]>
Acked-by: Kiryl Shutsemau <[email protected]>
Reviewed-by: Mike Rapoport (Microsoft) <[email protected]>
Reviewed-by: Lorenzo Stoakes <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Alistair Popple <[email protected]>
Cc: Andrey Konovalov <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: "Aneesh Kumar K.V" <[email protected]>
Cc: Anshuman Khandual <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: bibo mao <[email protected]>
Cc: Borislav Betkov <[email protected]>
Cc: Christoph Lameter (Ampere) <[email protected]>
Cc: Dennis Zhou <[email protected]>
Cc: Dev Jain <[email protected]>
Cc: Dmitriy Vyukov <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jane Chu <[email protected]>
Cc: Joao Martins <[email protected]>
Cc: Joerg Roedel <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: Kevin Brodsky <[email protected]>
Cc: Liam Howlett <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Oscar Salvador <[email protected]>
Cc: Peter Xu <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Qi Zheng <[email protected]>
Cc: Ryan Roberts <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Thomas Gleinxer <[email protected]>
Cc: Thomas Huth <[email protected]>
Cc: "Uladzislau Rezki (Sony)" <[email protected]>
Cc: Vincenzo Frascino <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: hygoni

arch/x86/include/asm/pgtable_64_types.h

@@ -36,6 +36,9 @@ static inline bool pgtable_l5_enabled(void)
 #define pgtable_l5_enabled() cpu_feature_enabled(X86_FEATURE_LA57)
 #endif /* USE_EARLY_PGTABLE_L5 */
 
+#define ARCH_PAGE_TABLE_SYNC_MASK \
+	(pgtable_l5_enabled() ? PGTBL_PGD_MODIFIED : PGTBL_P4D_MODIFIED)
+
 extern unsigned int pgdir_shift;
 extern unsigned int ptrs_per_p4d;
 

arch/x86/mm/init_64.c

@@ -223,6 +223,24 @@ static void sync_global_pgds(unsigned long start, unsigned long end)
 		sync_global_pgds_l4(start, end);
 }
 
+/*
+ * Make kernel mappings visible in all page tables in the system.
+ * This is necessary except when the init task populates kernel mappings
+ * during the boot process. In that case, all processes originating from
+ * the init task copies the kernel mappings, so there is no issue.
+ * Otherwise, missing synchronization could lead to kernel crashes due
+ * to missing page table entries for certain kernel mappings.
+ *
+ * Synchronization is performed at the top level, which is the PGD in
+ * 5-level paging systems. But in 4-level paging systems, however,
+ * pgd_populate() is a no-op, so synchronization is done at the P4D level.
+ * sync_global_pgds() handles this difference between paging levels.
+ */
+void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
+{
+	sync_global_pgds(start, end);
+}
+
 /*
  * NOTE: This function is marked __ref because it calls __init function
  * (alloc_bootmem_pages). It's safe to do it ONLY when after_bootmem == 0.