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* [RFC 0/2] mm/ptdump: Drop assumption that pxd_val() is u64
@ 2025-03-10  9:59 Anshuman Khandual
  2025-03-10  9:59 ` [RFC 1/2] mm/ptdump: Split note_page() into level specific callbacks Anshuman Khandual
  2025-03-10  9:59 ` [RFC 2/2] arm64/ptdump: Replace u64 with pteval_t Anshuman Khandual
  0 siblings, 2 replies; 3+ messages in thread
From: Anshuman Khandual @ 2025-03-10  9:59 UTC (permalink / raw)
  To: linux-mm
  Cc: Anshuman Khandual, Catalin Marinas, Will Deacon,
	Madhavan Srinivasan, Nicholas Piggin, Paul Walmsley,
	Palmer Dabbelt, Gerald Schaefer, Heiko Carstens, Peter Zijlstra,
	Thomas Gleixner, Ingo Molnar, Andrew Morton, linux-arm-kernel,
	linux-kernel, linuxppc-dev, linux-riscv, linux-s390

Last argument passed down in note_page() is u64 assuming pxd_val() returned
value (all page table levels) is 64 bit - which might not be the case going
ahead when D128 page tables is enabled on arm64 platform. Besides pxd_val()
is very platform specific and its type should not be assumed in generic MM.

This series splits note_page() into individual page table level specific
callbacks which accepts corresponding pxd_t page table entry as an argument
instead and later all subscribing platforms could derive pxd_val() from the
entries as required and proceed as before.

Page table entry's value, mask and protection are represented with pteval_t
not u64 that has been assumed while dumping the page table entries on arm64
platform. Replace such u64 instances with pteval_t instead as expected.

This series has been lightly tested on arm64 platform but it does build on
other relevant platforms (v6.14-rc5).

Some questions:

- Is there a better method to address this problem than splitting current
  note_page() into multiple call backs as proposed here ?

- This replaces note_page(st, 0, -1, 0) with note_page_pte(st, 0, pte_zero)
  Is that problematic ? Does level = -1 has got a special meaning ? Should
  level = -1 case be handled differently possibly via a separate callback ?

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-riscv@lists.infradead.org
Cc: linux-s390@vger.kernel.org
Cc: linux-mm@kvack.org

Anshuman Khandual (2):
  mm/ptdump: Split note_page() into level specific callbacks
  arm64/ptdump: Replace u64 with pteval_t

 arch/arm64/include/asm/ptdump.h | 22 ++++++++++++-----
 arch/arm64/mm/ptdump.c          | 41 ++++++++++++++++++++++++++++---
 arch/powerpc/mm/ptdump/ptdump.c | 37 ++++++++++++++++++++++++++--
 arch/riscv/mm/ptdump.c          | 37 ++++++++++++++++++++++++++--
 arch/s390/mm/dump_pagetables.c  | 37 ++++++++++++++++++++++++++--
 arch/x86/mm/dump_pagetables.c   | 31 +++++++++++++++++++++++-
 include/linux/ptdump.h          |  7 ++++--
 mm/ptdump.c                     | 43 +++++++++++++++++++++++++--------
 8 files changed, 226 insertions(+), 29 deletions(-)

-- 
2.25.1



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-- links below jump to the message on this page --
2025-03-10  9:59 [RFC 0/2] mm/ptdump: Drop assumption that pxd_val() is u64 Anshuman Khandual
2025-03-10  9:59 ` [RFC 1/2] mm/ptdump: Split note_page() into level specific callbacks Anshuman Khandual
2025-03-10  9:59 ` [RFC 2/2] arm64/ptdump: Replace u64 with pteval_t Anshuman Khandual

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