[PATCH v2 00/11] arm64: ptdump: View the second stage page-tables

Sebastian Ene
2023-10-19T14:40:50Z

Hi,

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

From the previous feedback I re-worked the series and added support for
guest page-tables dumping under VHE & nVHE configuration. I extended the
list of reviewers as I missed the interested parties in the first round.

When CONFIG_NVHE_EL2_PTDUMP_DEBUGFS is enabled under pKVM environment,
ptdump registers the 'host_stage2_kernel_page_tables' entry with debugfs.
Guests are registering a file named '%u_guest_stage2_page_tables' when
they are created.

This allows us to dump the host stage-2 page-tables with the following command:
cat /sys/kernel/debug/host_stage2_kernel_page_tables.

The output is showing the entries in the following format:
<IPA range> <size> <descriptor type> <access permissions> <mem_attributes>

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

Changelog:
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 (11):
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: Introduce stage-2 pagetables format description
arm64: ptdump: Add hooks on debugfs file operations
arm64: ptdump: Register a debugfs entry for the host stage-2
page-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 | 12 +
arch/arm64/kvm/hyp/include/nvhe/mem_protect.h | 8 +-
arch/arm64/kvm/hyp/nvhe/hyp-main.c | 18 +
arch/arm64/kvm/hyp/nvhe/mem_protect.c | 103 ++++
arch/arm64/kvm/hyp/pgtable.c | 98 ++--
arch/arm64/kvm/mmu.c | 3 +
arch/arm64/mm/ptdump.c | 487 +++++++++++++++++-
arch/arm64/mm/ptdump_debugfs.c | 42 +-
11 files changed, 822 insertions(+), 62 deletions(-)

--
2.42.0.655.g421f12c284-goog