mbox series

[v3,0/4] arch, mm: improve robustness of direct map manipulation

Message ID 20201101170815.9795-1-rppt@kernel.org (mailing list archive)
Headers show
Series arch, mm: improve robustness of direct map manipulation | expand

Message

Mike Rapoport Nov. 1, 2020, 5:08 p.m. UTC 
From: Mike Rapoport <rppt@linux.ibm.com>

Hi,

During recent discussion about KVM protected memory, David raised a concern
about usage of __kernel_map_pages() outside of DEBUG_PAGEALLOC scope [1].

Indeed, for architectures that define CONFIG_ARCH_HAS_SET_DIRECT_MAP it is
possible that __kernel_map_pages() would fail, but since this function is
void, the failure will go unnoticed.

Moreover, there's lack of consistency of __kernel_map_pages() semantics
across architectures as some guard this function with
#ifdef DEBUG_PAGEALLOC, some refuse to update the direct map if page
allocation debugging is disabled at run time and some allow modifying the
direct map regardless of DEBUG_PAGEALLOC settings.

This set straightens this out by restoring dependency of
__kernel_map_pages() on DEBUG_PAGEALLOC and updating the call sites
accordingly. 

Since currently the only user of __kernel_map_pages() outside
DEBUG_PAGEALLOC, it is updated to make direct map accesses there more
explicit.

[1] https://lore.kernel.org/lkml/2759b4bf-e1e3-d006-7d86-78a40348269d@redhat.com

v3 changes:
* update arm64 changes to avoid regression, per Rick's comments
* fix bisectability

v2 changes:
* Rephrase patch 2 changelog to better describe the change intentions and
implications
* Move removal of kernel_map_pages() from patch 1 to patch 2, per David
https://lore.kernel.org/lkml/20201029161902.19272-1-rppt@kernel.org

v1:
https://lore.kernel.org/lkml/20201025101555.3057-1-rppt@kernel.org

Mike Rapoport (4):
  mm: introduce debug_pagealloc_map_pages() helper
  PM: hibernate: make direct map manipulations more explicit
  arch, mm: restore dependency of __kernel_map_pages() of DEBUG_PAGEALLOC
  arch, mm: make kernel_page_present() always available

 arch/Kconfig                        |  3 +++
 arch/arm64/Kconfig                  |  4 +---
 arch/arm64/include/asm/cacheflush.h |  1 +
 arch/arm64/mm/pageattr.c            |  6 +++--
 arch/powerpc/Kconfig                |  5 +----
 arch/riscv/Kconfig                  |  4 +---
 arch/riscv/include/asm/pgtable.h    |  2 --
 arch/riscv/include/asm/set_memory.h |  1 +
 arch/riscv/mm/pageattr.c            | 31 +++++++++++++++++++++++++
 arch/s390/Kconfig                   |  4 +---
 arch/sparc/Kconfig                  |  4 +---
 arch/x86/Kconfig                    |  4 +---
 arch/x86/include/asm/set_memory.h   |  1 +
 arch/x86/mm/pat/set_memory.c        |  4 ++--
 include/linux/mm.h                  | 35 +++++++++++++----------------
 include/linux/set_memory.h          |  5 +++++
 kernel/power/snapshot.c             | 30 +++++++++++++++++++++++--
 mm/memory_hotplug.c                 |  3 +--
 mm/page_alloc.c                     |  6 ++---
 mm/slab.c                           |  8 +++----
 20 files changed, 103 insertions(+), 58 deletions(-)

Comments

Kirill A. Shutemov Nov. 3, 2020, 11:15 a.m. UTC | #1 
On Sun, Nov 01, 2020 at 07:08:11PM +0200, Mike Rapoport wrote:
> Mike Rapoport (4):
>   mm: introduce debug_pagealloc_map_pages() helper
>   PM: hibernate: make direct map manipulations more explicit
>   arch, mm: restore dependency of __kernel_map_pages() of DEBUG_PAGEALLOC
>   arch, mm: make kernel_page_present() always available

The series looks good to me (apart from the minor nit):

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>