Hi Oliver, On Fri, May 29, 2026 at 02:38:53PM +0100, Wei-Lin Chang wrote: > Hi Oliver, > > On Tue, May 19, 2026 at 02:31:09PM -0700, Oliver Upton wrote: > > 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/[email protected]/ > > Thanks for the pointer, I see, only inner/outer shareable, write-back > normal memory guarantees atomics to work. Interestingly, treating the > atomic instruction as a NOP is one of the permitted outcomes if other > memory attributes are used... > > However, the L2s in this series aren't using atomic instructions, and > right now for the current organization of this series, the L1 guest > hypervisor infrastructure is in lib/ for future NV selftests to share L2 > creation code, but L2 code are entirely per selftest. This means other > selftest L2s can reuse the L1 stage-1 tables themselves if the implicit > memory attributes that comes from MMU being off is not desired. > > Sorry if that sounded defensive, I am not opposed to always reusing the > L1 stage-1 tables in L2, just wanted to make sure the point gets across. > > Always reusing L1 stage-1 tables in L2 allows L2 access to lib/ (which > should be helpful for testing recursive NV), and L1-L2 code sharing > intra-selftest. OTOH things are a bit simpler with MMU off in this case > with testing the shadow stage2. > > What do you think?
Gentle ping on this :) Would love to hear what you think. Thanks, Wei-Lin Chang > > Thanks, > Wei-Lin Chang > > > > > 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/[email protected]/ > > > > > > 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 > > > > > >
