On Wed, 31 Jul 2019 16:46:01 +0100 Steven Price [off-list ref] wrote:

Make use of the new functionality in walk_page_range to remove the
arch page walking code and use the generic code to walk the page tables.

The effective permissions are passed down the chain using new fields
in struct pg_state.

The KASAN optimisation is implemented by including test_p?d callbacks
which can decide to skip an entire tree of entries

...

+static const struct ptdump_range ptdump_ranges[] = {
+#ifdef CONFIG_X86_64
 
-#define pgd_large(a) (pgtable_l5_enabled() ? pgd_large(a) : p4d_large(__p4d(pgd_val(a))))
-#define pgd_none(a)  (pgtable_l5_enabled() ? pgd_none(a) : p4d_none(__p4d(pgd_val(a))))
+#define normalize_addr_shift (64 - (__VIRTUAL_MASK_SHIFT + 1))
+#define normalize_addr(u) ((signed long)(u << normalize_addr_shift) \
+				>> normalize_addr_shift)
 
-static inline bool is_hypervisor_range(int idx)
-{
-#ifdef CONFIG_X86_64
-	/*
-	 * A hole in the beginning of kernel address space reserved
-	 * for a hypervisor.
-	 */
-	return	(idx >= pgd_index(GUARD_HOLE_BASE_ADDR)) &&
-		(idx <  pgd_index(GUARD_HOLE_END_ADDR));
+	{0, PTRS_PER_PGD * PGD_LEVEL_MULT / 2},
+	{normalize_addr(PTRS_PER_PGD * PGD_LEVEL_MULT / 2), ~0UL},

This blows up because PGD_LEVEL_MULT is sometimes not a constant.

x86_64 allmodconfig:

In file included from ./arch/x86/include/asm/pgtable_types.h:249:0,
                 from ./arch/x86/include/asm/paravirt_types.h:45,
                 from ./arch/x86/include/asm/ptrace.h:94,
                 from ./arch/x86/include/asm/math_emu.h:5,
                 from ./arch/x86/include/asm/processor.h:12,
                 from ./arch/x86/include/asm/cpufeature.h:5,
                 from ./arch/x86/include/asm/thread_info.h:53,
                 from ./include/linux/thread_info.h:38,
                 from ./arch/x86/include/asm/preempt.h:7,
                 from ./include/linux/preempt.h:78,
                 from ./include/linux/spinlock.h:51,
                 from ./include/linux/wait.h:9,
                 from ./include/linux/wait_bit.h:8,
                 from ./include/linux/fs.h:6,
                 from ./include/linux/debugfs.h:15,
                 from arch/x86/mm/dump_pagetables.c:11:
./arch/x86/include/asm/pgtable_64_types.h:56:22: error: initializer element is not constant
 #define PTRS_PER_PGD 512
                      ^
arch/x86/mm/dump_pagetables.c:363:6: note: in expansion of macro ‘PTRS_PER_PGD’
  {0, PTRS_PER_PGD * PGD_LEVEL_MULT / 2},
      ^~~~~~~~~~~~
./arch/x86/include/asm/pgtable_64_types.h:56:22: note: (near initialization for ‘ptdump_ranges[0].end’)
 #define PTRS_PER_PGD 512
                      ^
arch/x86/mm/dump_pagetables.c:363:6: note: in expansion of macro ‘PTRS_PER_PGD’
  {0, PTRS_PER_PGD * PGD_LEVEL_MULT / 2},
      ^~~~~~~~~~~~
arch/x86/mm/dump_pagetables.c:360:27: error: initializer element is not constant
 #define normalize_addr(u) ((signed long)(u << normalize_addr_shift) \
                           ^
arch/x86/mm/dump_pagetables.c:364:3: note: in expansion of macro ‘normalize_addr’
  {normalize_addr(PTRS_PER_PGD * PGD_LEVEL_MULT / 2), ~0UL},
   ^~~~~~~~~~~~~~
arch/x86/mm/dump_pagetables.c:360:27: note: (near initialization for ‘ptdump_ranges[1].start’)
 #define normalize_addr(u) ((signed long)(u << normalize_addr_shift) \
                           ^
arch/x86/mm/dump_pagetables.c:364:3: note: in expansion of macro ‘normalize_addr’
  {normalize_addr(PTRS_PER_PGD * PGD_LEVEL_MULT / 2), ~0UL},

I don't know what to do about this so I'll drop the series.

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