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* [PATCH v2 0/4] arch, mm: improve robustness of direct map manipulation
@ 2020-10-29 16:18 Mike Rapoport
  2020-10-29 16:18 ` [PATCH v2 1/4] mm: introduce debug_pagealloc_map_pages() helper Mike Rapoport
                   ` (3 more replies)
  0 siblings, 4 replies; 6+ messages in thread
From: Mike Rapoport @ 2020-10-29 16:18 UTC (permalink / raw)
  To: Andrew Morton
  Cc: David Hildenbrand, Peter Zijlstra, Dave Hansen, linux-mm,
	Paul Mackerras, Pavel Machek, H. Peter Anvin, sparclinux,
	Christoph Lameter, Will Deacon, linux-riscv, linux-s390, x86,
	Mike Rapoport, Christian Borntraeger, Ingo Molnar,
	Catalin Marinas, Len Brown, Albert Ou, Vasily Gorbik, linux-pm,
	Heiko Carstens, David Rientjes, Borislav Petkov, Andy Lutomirski,
	Paul Walmsley, Kirill A. Shutemov, Thomas Gleixner,
	linux-arm-kernel, Rafael J. Wysocki, linux-kernel, Pekka Enberg,
	Palmer Dabbelt, Joonsoo Kim, Edgecombe, Rick P, linuxppc-dev,
	David S. Miller, Mike Rapoport

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

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

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


^ permalink raw reply	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2020-10-29 16:51 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-10-29 16:18 [PATCH v2 0/4] arch, mm: improve robustness of direct map manipulation Mike Rapoport
2020-10-29 16:18 ` [PATCH v2 1/4] mm: introduce debug_pagealloc_map_pages() helper Mike Rapoport
2020-10-29 16:19 ` [PATCH v2 2/4] PM: hibernate: make direct map manipulations more explicit Mike Rapoport
2020-10-29 16:30   ` Rafael J. Wysocki
2020-10-29 16:19 ` [PATCH v2 3/4] arch, mm: restore dependency of __kernel_map_pages() of DEBUG_PAGEALLOC Mike Rapoport
2020-10-29 16:19 ` [PATCH v2 4/4] arch, mm: make kernel_page_present() always available Mike Rapoport

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