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

Message

Ricardo Koller Sept. 20, 2022, 4:14 a.m. UTC

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/[e-mail]/
- 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/[e-mail]/
- 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/[e-mail]/
- 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

Comments

Ricardo Koller Sept. 20, 2022, 4:18 a.m. UTC | #1

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/[e-mail]/
> - 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/[e-mail]/
> - 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/[e-mail]/
> - 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!