[PATCH v9 0/5] arm64: ptdump: View the second stage page-tables

Tue Aug 27 01:45:43 PDT 2024

Hi,

This series extends the ptdump support to allow dumping the guest
stage-2 pagetables. When CONFIG_PTDUMP_STAGE2_DEBUGFS is enabled, ptdump
registers the new following files under debugfs:
- /sys/debug/kvm/<guest_id>/stage2_page_tables
- /sys/debug/kvm/<guest_id>/stage2_levels
- /sys/debug/kvm/<guest_id>/ipa_range

This allows userspace tools (eg. cat) to dump the stage-2 pagetables by
reading the 'stage2_page_tables' file.
The output format has the following fields:
<IPA range> <size> <level> <access permissions> <mem_attributes>

Below is the output of a guest stage-2 pagetable dump running under Qemu.
After a VM is created, the following files are available:

# cat /sys/kernel/debug/kvm/256-4/stage2_levels 
4
# cat /sys/kernel/debug/kvm/256-4/ipa_range 
44
# cat /sys/kernel/debug/kvm/256-4/stage2_page_tables 
---[ Guest IPA ]---
0x0000000000000000-0x0000000001000000          16M 2
0x0000000001000000-0x0000000001020000         128K 3
0x0000000001020000-0x0000000001021000           4K 3   R W X AF    
0x0000000001021000-0x0000000001200000        1916K 3
0x0000000001200000-0x0000000040000000        1006M 2
0x0000000040000000-0x0000000080000000           1G 0
0x0000000080000000-0x0000000081200000          18M 2   R W   AF BLK
0x0000000081200000-0x0000000081a00000           8M 2   R W X AF BLK
0x0000000081a00000-0x0000000081c00000           2M 2   R W   AF BLK
0x0000000081c00000-0x0000000082200000           6M 2   R W X AF BLK
0x0000000082200000-0x0000000082400000           2M 2   R W   AF BLK
0x0000000082400000-0x0000000082800000           4M 2   R W X AF BLK
0x0000000082800000-0x0000000082a00000           2M 2   R W   AF BLK
0x0000000082a00000-0x0000000082c00000           2M 2
0x0000000082c00000-0x0000000083200000           6M 2   R W X AF BLK
0x0000000083200000-0x0000000083400000           2M 2
0x0000000083400000-0x0000000083a00000           6M 2   R W X AF BLK
0x0000000083a00000-0x000000008fe00000         196M 2
0x000000008fe00000-0x0000000090000000           2M 2   R W   AF BLK
0x0000000090000000-0x0000000099400000         148M 2
0x0000000099400000-0x0000000099600000           2M 2   R W X AF BLK
0x0000000099600000-0x000000009b600000          32M 2
0x000000009b600000-0x000000009be00000           8M 2   R W X AF BLK
0x000000009be00000-0x000000009c000000           2M 2   R W   AF BLK
0x000000009c000000-0x00000000c0000000         576M 2

Changelog:
v8 -> current:
 * squashed the last 3 patches and separated the Kconfig change as the
   last patch.
 * updated the commit message of the 3rd patch
 * printing level numbers instead of names as suggested by Mark
 * fixed one return code to ERR_PTR(-ENOMEM) as spotted by Vincent
 * dropped a barely empty header 'kvm_ptdump.h'
 * general cosmetic changes 

v7 -> v8:
 * applied Will's feedback and prefixed the exported structure names
   with ptdump_
 * dropped PTE_CONT and PTE_NG attribute parsing from Oliver's
   suggestion
 * fixed spurious BLK annotation reported by Vincent
 * repurposed `stage2_levels` debugfs file to show the number of the
   levels
 * tried changing the order of the patches:
   "5/6 Initialize the ptdump parser with stage-2 attributes" before
   exposing the debugfs file but ended up keeping the same order
   as this depends on the later one.

 v6 -> v7:
 * Reworded commit for this patch : [PATCH v6 2/6] arm64: ptdump: Expose
   the attribute parsing functionality
 * fixed minor conflicts in the struct pg_state definition
 * moved the kvm_ptdump_guest_registration in the
 * kvm_arch_create_vm_debugfs
 * reset the parse state before walking the pagetables
 * copy the level name to the pg_level buffer

 v5 -> v6:
 * don't return an error if the kvm_arch_create_vm_debugfs fails to
   initialize (ref.
https://lore.kernel.org/all/20240216155941.2029458-1-oliver.upton@linux.dev/)  
 * fix use-after-free suggested by getting a reference to the
   KVM struct while manipulating the debugfs files
   and put the reference on the file close.
 * do all the allocations at once for the ptdump parser state tracking
   and simplify the initialization.
 * move the ptdump parser state initialization as part of the file_open
 * create separate files for printing the guest stage-2 pagetable
   configuration such as: the start level of the pagetable walk and the
   number of bits used for the IPA space representation.
 * fixed the wrong header format for the newly added file
 * include missing patch which hasn't been posted on the v5:
   "KVM-arm64-Move-pagetable-definitions-to-common-heade.patch" 

Links to previous versions:
v8:
https://lore.kernel.org/all/20240816123906.3683425-1-sebastianene@google.com/  
v7:
https://lore.kernel.org/all/20240621123230.1085265-1-sebastianene@google.com/
v6:
https://lore.kernel.org/all/20240220151035.327199-1-sebastianene@google.com/
v5:
https://lore.kernel.org/all/20240207144832.1017815-2-sebastianene@google.com/

Thanks,
Sebastian

Sebastian Ene (5):
  KVM: arm64: Move pagetable definitions to common header
  arm64: ptdump: Expose the attribute parsing functionality
  arm64: ptdump: Use the ptdump description from a local context
  KVM: arm64: Register ptdump with debugfs on guest creation
  KVM: arm64: Introduce the PTDUMP_STAGE2_DEBUGFS config

 arch/arm64/include/asm/kvm_host.h    |   6 +
 arch/arm64/include/asm/kvm_pgtable.h |  42 +++++
 arch/arm64/include/asm/ptdump.h      |  42 ++++-
 arch/arm64/kvm/Kconfig               |  17 ++
 arch/arm64/kvm/Makefile              |   1 +
 arch/arm64/kvm/arm.c                 |   1 +
 arch/arm64/kvm/hyp/pgtable.c         |  42 -----
 arch/arm64/kvm/ptdump.c              | 247 +++++++++++++++++++++++++++
 arch/arm64/mm/ptdump.c               |  66 ++-----
 9 files changed, 373 insertions(+), 91 deletions(-)
 create mode 100644 arch/arm64/kvm/ptdump.c

-- 
2.46.0.295.g3b9ea8a38a-goog