Re: [PATCH v6 00/13] KVM: selftests: Add aarch64/page_fault_test

[Ricardo Koller <ricarkol@google.com>]

On Tue, Sep 20, 2022 at 04:14:56AM +0000, Ricardo Koller wrote:
> This series adds a new aarch64 selftest for testing stage 2 fault handling for
> various combinations of guest accesses (e.g., write, S1PTW), backing sources
> (e.g., anon), and types of faults (e.g., read on hugetlbfs with a hole, write
> on a readonly memslot). Each test tries a different combination and then checks
> that the access results in the right behavior (e.g., uffd faults with the right
> address and write/read flag). Some interesting combinations are:
> 
> - loading an instruction leads to a stage 1 page-table-walk that misses on
>   stage 2 because the backing memslot for the page table it not in host memory
>   (a hole was punched right there) and the fault is handled using userfaultfd.
>   The expected behavior is that this leads to a userfaultfd fault marked as a
>   write. See commit c4ad98e4b72c ("KVM: arm64: Assume write fault on S1PTW
>   permission fault on instruction fetch") for why that's a write.
> - a cas (compare-and-swap) on a readonly memslot leads to a failed vcpu run.
> - write-faulting on a memslot that's marked for userfaultfd handling and dirty
>   logging should result in a uffd fault and having the respective bit set in
>   the dirty log.
> 
> The first 8 commits of this series add library support. The first one adds a
> new userfaultfd library. Commits 2-5 add some misc library changes that will be
> used by the new test, like a library function to get the GPA of a PTE. Commits
> 6-8 breaks the implicit assumption that code and page tables live in memslot
> memslots should allocators use. This is then used by the new test to place the
> page tables in a specific memslot.  The last 5 commits add the new selftest,
> one type of test at a time. It first adds core tests, then uffd, then dirty
> logging, then readonly memslots tests, and finally combinations of the previous
> ones (like uffd and dirty logging at the same time).
> 
> v6 -> v7: https://lore.kernel.org/kvmarm/Yyi03sX5hx36M%2FZr@google.com/
> - removed struct kvm_vm_mem_params. Changed page_fault_test.c accordingly. [Sean]
> - applied Oliver's patch to fix page_fault_test compilation warnings. [Oliver]
> - added R-b's from Oliver and Andrew. Didn't Andrew's R-b on 6/13 as the commit
>   changed afterwards.
> 
> v5 -> v6: https://lore.kernel.org/kvmarm/20220823234727.621535-1-ricarkol@google.com/
> - added "enum memslot_type" and all the related cleanups due to it [Andrew]
> - default kvm_vm_mem_default with size=0 [Andrew,Sean]
> - __vm_vaddr_alloc() taking "enum memslot_type" and all the related cleanups
>   due to this change [Andrew]
> 
> v4 -> v5: https://lore.kernel.org/kvmarm/20220624213257.1504783-1-ricarkol@google.com/
> - biggest change: followed suggestion from Sean and Andrew regarding a new
>   arg for vm_create() to specify the guest memory layout. That's taken care
>   of with these two new commits:
> 	KVM: selftests: Use the right memslot for code, page-tables, and data allocations
> 	KVM: selftests: Change ____vm_create() to take struct kvm_vm_mem_params
>   plus the respective changes in the page_fault_test itself (mostly code reduction).
> - dropped some commits that are not needed after the above change:
> 	KVM: selftests: aarch64: Export _virt_pg_map with a pt_memslot arg
> 	KVM: selftests: Add vm_alloc_page_table_in_memslot library function
> 	KVM: selftests: Add vm_mem_region_get_src_fd library function
> - addressed Oliver comments in commit "KVM: selftests: aarch64: Add
>   aarch64/page_fault_test"
> - collect r-b's from Andrew
> 
> Ricardo Koller (13):
>   KVM: selftests: Add a userfaultfd library
>   KVM: selftests: aarch64: Add virt_get_pte_hva() library function
>   KVM: selftests: Add missing close and munmap in
>     __vm_mem_region_delete()
>   KVM: selftests: aarch64: Construct DEFAULT_MAIR_EL1 using sysreg.h
>     macros
>   tools: Copy bitfield.h from the kernel sources
>   KVM: selftests: Stash backing_src_type in struct userspace_mem_region
>   KVM: selftests: Add vm->memslots[] and enum kvm_mem_region_type
>   KVM: selftests: Use the right memslot for code, page-tables, and data
>     allocations
>   KVM: selftests: aarch64: Add aarch64/page_fault_test
>   KVM: selftests: aarch64: Add userfaultfd tests into page_fault_test
>   KVM: selftests: aarch64: Add dirty logging tests into page_fault_test
>   KVM: selftests: aarch64: Add readonly memslot tests into
>     page_fault_test
>   KVM: selftests: aarch64: Add mix of tests into page_fault_test
> 
>  tools/include/linux/bitfield.h                |  176 +++
>  tools/testing/selftests/kvm/.gitignore        |    1 +
>  tools/testing/selftests/kvm/Makefile          |    2 +
>  .../selftests/kvm/aarch64/page_fault_test.c   | 1116 +++++++++++++++++
>  .../selftests/kvm/demand_paging_test.c        |  228 +---
>  .../selftests/kvm/include/aarch64/processor.h |   35 +-
>  .../selftests/kvm/include/kvm_util_base.h     |   29 +-
>  .../selftests/kvm/include/userfaultfd_util.h  |   45 +
>  .../selftests/kvm/lib/aarch64/processor.c     |   26 +-
>  tools/testing/selftests/kvm/lib/elf.c         |    3 +-
>  tools/testing/selftests/kvm/lib/kvm_util.c    |   82 +-
>  .../selftests/kvm/lib/riscv/processor.c       |    7 +-
>  .../selftests/kvm/lib/s390x/processor.c       |    7 +-
>  .../selftests/kvm/lib/userfaultfd_util.c      |  186 +++
>  .../selftests/kvm/lib/x86_64/processor.c      |   13 +-
>  15 files changed, 1698 insertions(+), 258 deletions(-)
>  create mode 100644 tools/include/linux/bitfield.h
>  create mode 100644 tools/testing/selftests/kvm/aarch64/page_fault_test.c
>  create mode 100644 tools/testing/selftests/kvm/include/userfaultfd_util.h
>  create mode 100644 tools/testing/selftests/kvm/lib/userfaultfd_util.c
> 
> -- 
> 2.37.3.968.ga6b4b080e4-goog
> 

Please ignore this v6 series (It should have been v7). Sending the real
v7 in a bit. Thanks and sorry for the mess!