Messages in this thread | ![/](/images/icornerl.gif) | | Date | Mon, 18 Dec 2023 13:58:50 +0000 | Subject | [PATCH v4 00/10] arm64: ptdump: View the second stage page-tables | From | Sebastian Ene <> |
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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 third version: https://lore.kernel.org/all/20231115171639.2852644-2-sebastianene@google.com/
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: v3 -> current_version: * refactorization: moved all the **KVM** specific components under kvm/ as suggested by Oliver. Introduced a new file arm64/kvm/ptdump.c which handled the second stage translation. re-used only the display portion from mm/ptdump.c
* pagetable snapshot creation now uses memory donated from the host. The memory is no longer shared with the host as this can pose a security risk if the host has access to manipulate the pagetable copy while the hypervisor iterates it.
* fixed a memory leak: while memory was used from the memcache for building the snapshot pagetable, it was no longer giving back the pages to the host for freeing. A separate array was introduced to keep track of the pages allocated from the memcache.
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 snapshot interface for the host stage-2 pagetable KVM: arm64: Add ptdump registration with debugfs for the stage-2 pagetables KVM: arm64: Invoke the snapshot interface for the host stage-2 pagetable arm64: ptdump: Expose the attribute parsing functionality arm64: ptdump: Use the mask from the state structure KVM: arm64: Move pagetable definitions to common header KVM: arm64: Walk the pagetable snapshot and parse the ptdump descriptors arm64: ptdump: Interpret memory attributes based on the runtime config arm64: ptdump: Interpret pKVM ownership annotations arm64: ptdump: Add guest stage-2 pagetables dumping
arch/arm64/include/asm/kvm_asm.h | 1 + arch/arm64/include/asm/kvm_pgtable.h | 111 +++++ arch/arm64/include/asm/ptdump.h | 49 +- arch/arm64/kvm/Kconfig | 13 + arch/arm64/kvm/Makefile | 1 + arch/arm64/kvm/arm.c | 2 + arch/arm64/kvm/debug.c | 6 + arch/arm64/kvm/hyp/include/nvhe/mem_protect.h | 27 +- arch/arm64/kvm/hyp/nvhe/hyp-main.c | 12 + arch/arm64/kvm/hyp/nvhe/mem_protect.c | 186 ++++++++ arch/arm64/kvm/hyp/pgtable.c | 85 ++-- arch/arm64/kvm/kvm_ptdump.h | 21 + arch/arm64/kvm/ptdump.c | 436 ++++++++++++++++++ arch/arm64/mm/ptdump.c | 55 +-- 14 files changed, 897 insertions(+), 108 deletions(-) create mode 100644 arch/arm64/kvm/kvm_ptdump.h create mode 100644 arch/arm64/kvm/ptdump.c
-- 2.43.0.472.g3155946c3a-goog
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