On 8/2/21 11:34 AM, Gavin Shan wrote:

There are couple of issues with current implementations and this series
tries to resolve the issues:

  (a) All needed information are scattered in variables, passed to various
      test functions. The code is organized in pretty much relaxed fashion.

  (b) The page isn't allocated from buddy during page table entry modifying
      tests. The page can be invalid, conflicting to the implementations
      of set_xxx_at() on ARM64. The target page is accessed so that the
      iCache can be flushed when execution permission is given on ARM64.
      Besides, the target page can be unmapped and accessing to it causes
      kernel crash.

"struct pgtable_debug_args" is introduced to address issue (a). For issue
(b), the used page is allocated from buddy in page table entry modifying
tests. The corresponding tets will be skipped if we fail to allocate the
(huge) page. For other test cases, the original page around to kernel
symbol (@start_kernel) is still used.

The patches are organized as below. PATCH[2-10] could be combined to one
patch, but it will make the review harder:

  PATCH[1] introduces "struct pgtable_debug_args" as place holder of all
           needed information. With it, the old and new implementation
           can coexist.
  PATCH[2-10] uses "struct pgtable_debug_args" in various test functions.
  PATCH[11] removes the unused code for old implementation.
  PATCH[12] fixes the issue of corrupted page flag for ARM64

Changelog
=========
v5:
   * Pick r-bs from Anshuman and rebase to 5.14.rc4          (Gavin)
   * Use args->start_p4dp to free p4d entries                (Anshuman)
   * Introduce helper to allocate huge page in init_arg()    (Anshuman)
   * Bail early if the allocated page doesn't exist in
     swap_migration_tests() and correct the comments         (Anshuman)
   * Add fixes tag to PATCH[v4 12/12]                        (Christophe)
   * Address misc comments                                   (Anshuman)

Apart from the proposed changes discussed for the first patch [PATCH 1/12],
this series overall looks good now. It clears build tests on all supported
platforms. I was able to test this on arm64 and x86 platforms with various
functional config combinations. It would be still great if others can take
a look as well.

- Anshuman