Hi Wei-Lin,
Thank you very much for the series.
I haven't had time to read through much of this yet, but I noticed
Itaru's comment about leaving stage-1 translation disabled for the L2.
Since selftests expects things like atomics to work we will definitely
need the stage-1 MMU to be enabled w/ Normal mappings (this was broken
in the past [*]). I wonder if we can (ab)use the pre-existing stage-1
tables that the selftests library creates on behalf of the L1. After all,
L1 and L2 are both effectively in the same virtual address space.
[*] https://lore.kernel.org/kvmarm/20250405001042.1470552-1-rananta@google.com/
Thanks,
Oliver
On Sat, May 16, 2026 at 07:29:54PM +0100, Wei-Lin Chang wrote:
> Hi,
>
> This is v3 of adding basic support for running nested guests (L2) in
> kselftest. This time a framework for enabling stage-2 in the guest is
> added, including the s2_mmu struct, s2 translation control setup, and
> a stage-2 page table generator. Similar to L2 vCPU management, all
> stage-2 work is done in the guest instead of userspace.
>
> An additional shadow_stage2 test is added which leverages the framework
> to run L2 with stage-2 enabled.
>
> * Changes from v2 [1]:
>
> - Update vm_paddr_t to gpa_t, vm_vaddr_t to gva_t.
>
> - Added framework for enabling stage-2 in the guest.
>
> - Added shadow_stage2 test.
>
> Thanks!
>
> [1]: https://lore.kernel.org/kvmarm/20260412142216.3806482-1-weilin.chang@arm.com/
>
> Wei-Lin Chang (9):
> KVM: arm64: selftests: Add GPR save/restore functions for NV
> KVM: arm64: selftests: Add helpers for guest hypervisors
> KVM: arm64: selftests: Add hello_nested basic NV selftest
> KVM: arm64: selftests: Enhance hello_nested test
> KVM: arm64: selftests: Add shadow_stage2 test
> KVM: arm64: selftests: shadow_stage2: Allocate L2 stack from dedicated
> pool
> KVM: arm64: selftests: shadow_stage2: Check supported stage-2 granule
> size
> KVM: arm64: selftests: Add infrastructure for using stage-2 in guest
> KVM: arm64: selftests: shadow_stage2: Turn on stage-2 translation for
> the nested guest
>
> tools/testing/selftests/kvm/Makefile.kvm | 5 +
> .../selftests/kvm/arm64/hello_nested.c | 134 +++++++++
> .../selftests/kvm/arm64/shadow_stage2.c | 165 +++++++++++
> .../selftests/kvm/include/arm64/nested.h | 85 ++++++
> tools/testing/selftests/kvm/lib/arm64/entry.S | 137 +++++++++
> .../selftests/kvm/lib/arm64/hyp-entry.S | 77 +++++
> .../testing/selftests/kvm/lib/arm64/nested.c | 264 ++++++++++++++++++
> 7 files changed, 867 insertions(+)
> create mode 100644 tools/testing/selftests/kvm/arm64/hello_nested.c
> create mode 100644 tools/testing/selftests/kvm/arm64/shadow_stage2.c
> create mode 100644 tools/testing/selftests/kvm/include/arm64/nested.h
> create mode 100644 tools/testing/selftests/kvm/lib/arm64/entry.S
> create mode 100644 tools/testing/selftests/kvm/lib/arm64/hyp-entry.S
> create mode 100644 tools/testing/selftests/kvm/lib/arm64/nested.c
>
> --
> 2.43.0
>
>