linux-kernel - [PATCH v3 00/10] arm64: ptdump: View the second stage page-tables

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Message-ID: <20231115171639.2852644-2-sebastianene@google.com>
Date:   Wed, 15 Nov 2023 17:16:30 +0000
From:   Sebastian Ene <sebastianene@...gle.com>
To:     will@...nel.org, Oliver Upton <oliver.upton@...ux.dev>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Zenghui Yu <yuzenghui@...wei.com>, catalin.marinas@....com,
        mark.rutland@....com, akpm@...ux-foundation.org, maz@...nel.org
Cc:     kvmarm@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        vdonnefort@...gle.com, qperret@...gle.com, smostafa@...gle.com,
        Sebastian Ene <sebastianene@...gle.com>
Subject: [PATCH v3 00/10] arm64: ptdump: View the second stage page-tables

Hi,

This can be used as a debugging tool for dumping the second stage
page-tables.

When CONFIG_PTDUMP_STAGE2_DEBUGFS is enabled, ptdump registers 
'/sys/debug/kvm/<guest_id>/stage2_page_tables' entry with debugfs
upon guest creation. This allows userspace tools (eg. cat) to dump the
stage-2 pagetables by reading the registered file.

Reading the debugfs file shows stage-2 memory ranges in following format:
<IPA range> <size> <descriptor type> <access permissions> <mem_attributes>

Under pKVM configuration(kvm-arm.mode=protected) ptdump registers an entry
for the host stage-2 pagetables in the following path:
/sys/debug/kvm/host_stage2_page_tables/

The tool interprets the pKVM ownership annotation stored in the invalid
entries and dumps to the console the ownership information. To be able
to access the host stage-2 page-tables from the kernel, a new hypervisor
call was introduced which allows us to snapshot the page-tables in a host
provided buffer. The hypervisor call is hidden behind CONFIG_NVHE_EL2_DEBUG
as this should be used under debugging environment.

Link to the second version:
https://lore.kernel.org/all/20231019144032.2943044-1-sebastianene@google.com/#r

Link to the first version:
https://lore.kernel.org/all/20230927112517.2631674-1-sebastianene@google.com/

Changelog:

  v2 -> v3:
  * register the stage-2 debugfs entry for the host under
    /sys/debug/kvm/host_stage2_page_tables and in
    /sys/debug/kvm/<guest_id>/stage2_page_tables for guests.

  * don't use a static array for parsing the attributes description,
    generate it dynamically based on the number of pagetable levels

  * remove the lock that was guarding the seq_file private inode data,
    and keep the data private to the open file session.

  * minor fixes & renaming of CONFIG_NVHE_EL2_PTDUMP_DEBUGFS to
    CONFIG_PTDUMP_STAGE2_DEBUGFS

  v1 -> v2:
  * use the stage-2 pagetable walker for dumping descriptors instead of
    the one provided by ptdump.

  * support for guests pagetables dumping under VHE/nVHE non-protected

Thanks,

Sebastian Ene (10):
  KVM: arm64: Add snap shooting the host stage-2 pagetables
  arm64: ptdump: Use the mask from the state structure
  arm64: ptdump: Add the walker function to the ptdump info structure
  KVM: arm64: Move pagetable definitions to common header
  arm64: ptdump: Add hooks on debugfs file operations
  arm64: ptdump: Register a debugfs entry for the host stage-2 tables
  arm64: ptdump: Parse the host stage-2 page-tables from the snapshot
  arm64: ptdump: Interpret memory attributes based on runtime
    configuration
  arm64: ptdump: Interpret pKVM ownership annotations
  arm64: ptdump: Add support for guest stage-2 pagetables dumping

 arch/arm64/include/asm/kvm_asm.h              |   1 +
 arch/arm64/include/asm/kvm_pgtable.h          |  85 +++
 arch/arm64/include/asm/ptdump.h               |  27 +
 arch/arm64/kvm/Kconfig                        |  13 +
 arch/arm64/kvm/arm.c                          |   2 +
 arch/arm64/kvm/debug.c                        |   6 +
 arch/arm64/kvm/hyp/include/nvhe/mem_protect.h |   8 +-
 arch/arm64/kvm/hyp/nvhe/hyp-main.c            |  20 +
 arch/arm64/kvm/hyp/nvhe/mem_protect.c         | 102 ++++
 arch/arm64/kvm/hyp/pgtable.c                  |  98 ++--
 arch/arm64/kvm/mmu.c                          |   2 +
 arch/arm64/mm/ptdump.c                        | 483 +++++++++++++++++-
 arch/arm64/mm/ptdump_debugfs.c                |  64 ++-
 13 files changed, 852 insertions(+), 59 deletions(-)

-- 
2.43.0.rc0.421.g78406f8d94-goog