[PATCH 0/3] KVM: arm64: selftests: Basic nested guest support

[Wei-Lin Chang <weilin.chang@arm.com>]

Hi,

This series adds basic support for running nested guests (L2) in
kselftest. The first patch adds library functions. While designing the
APIs for userspace, I referenced Joey's approach for kvm-unit-tests [1].
In summary, four preparatory functions are provided for userspace to
set up state to run an L2 in EL1:

 - prepare_l2_stack()            <- sets up stack for L2
 - prepare_hyp_state()           <- sets up vEL2 registers
 - prepare_eret_destination()    <- userspace passes a function pointer
                                    for L2 to run
 - prepare_nested_sync_handler() <- sets up hvc handler in order to
                                    regain control after L2's hvc

After calling those functions, userspace can vcpu_run(), and when
run_l2() is called within the guest, the supplied function will be run
in L2, with the control flow managed by the library code in nested.c and
nested_asm.S. After running the L2 function, run_l2() will automatically
return. Note that the L2 function supplied by the user does not have to
call hvc.

Patch 2 demonstrates usage of the APIs introduced above, with a simple
L1 -> L2 -> L1 sequence, with an empty L2 function.

Patch 3 enhances the library functions by setting up L2 -> L1 stage-2
translation. Currently the translation is simple, with start level 0, 4
levels, 4KB granules, normal cachable, 48-bit IA, 40-bit OA.

[1]: https://lore.kernel.org/kvmarm/20260306142656.2775185-1-joey.gouly@arm.com/

Wei-Lin Chang (3):
  KVM: arm64: selftests: Add library functions for NV
  KVM: arm64: sefltests: Add basic NV selftest
  KVM: arm64: selftests: Enable stage-2 in NV preparation functions

 tools/testing/selftests/kvm/Makefile.kvm      |   3 +
 .../selftests/kvm/arm64/hello_nested.c        |  65 ++++++++
 .../selftests/kvm/include/arm64/nested.h      |  25 +++
 .../selftests/kvm/include/arm64/processor.h   |   9 +
 .../testing/selftests/kvm/lib/arm64/nested.c  | 154 ++++++++++++++++++
 .../selftests/kvm/lib/arm64/nested_asm.S      |  35 ++++
 6 files changed, 291 insertions(+)
 create mode 100644 tools/testing/selftests/kvm/arm64/hello_nested.c
 create mode 100644 tools/testing/selftests/kvm/include/arm64/nested.h
 create mode 100644 tools/testing/selftests/kvm/lib/arm64/nested.c
 create mode 100644 tools/testing/selftests/kvm/lib/arm64/nested_asm.S

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2.43.0