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

* [PATCH v3 0/4] arch, mm: improve robustness of direct map manipulation
@ 2020-11-01 17:08 Mike Rapoport
  2020-11-01 17:08 ` [PATCH v3 1/4] mm: introduce debug_pagealloc_map_pages() helper Mike Rapoport
                   ` (4 more replies)
  0 siblings, 5 replies; 16+ messages in thread
From: Mike Rapoport @ 2020-11-01 17:08 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Albert Ou, Andy Lutomirski, Benjamin Herrenschmidt,
	Borislav Petkov, Catalin Marinas, Christian Borntraeger,
	Christoph Lameter, David S. Miller, Dave Hansen,
	David Hildenbrand, David Rientjes, Edgecombe, Rick P,
	H. Peter Anvin, Heiko Carstens, Ingo Molnar, Joonsoo Kim,
	Kirill A. Shutemov, Len Brown, Michael Ellerman, Mike Rapoport,
	Mike Rapoport, Palmer Dabbelt, Paul Mackerras, Paul Walmsley,
	Pavel Machek, Pekka Enberg, Peter Zijlstra, Rafael J. Wysocki,
	Thomas Gleixner, Vasily Gorbik, Will Deacon, linux-arm-kernel,
	linux-kernel, linux-mm, linux-pm, linux-riscv, linux-s390,
	linuxppc-dev, sparclinux, x86

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(-)

-- 
2.28.0

*** BLURB HERE ***

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(-)

-- 
2.28.0

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