From a4be8d69698b11d976c122be2d32bb72b8a52809 Mon Sep 17 00:00:00 2001 From: Sasha Levin Date: Sun, 25 Oct 2026 21:21:28 -0400 Subject: [PATCH] KVM: arm64: selftests: Skip unwritable ID fields in the failed-run test test_idreg_frozen_after_failed_run() checks that changing a feature ID register after a failed first KVM_RUN is rejected with -EBUSY, and does so for every field of every register in test_regs. On a host without AArch32 support at EL0, KVM treats the AArch32 ID registers as RAZ/WI: aa32_id_visibility() returns REG_RAZ | REG_USER_WI, and kvm_sys_reg_set_user() ignores the write and returns 0 before set_id_reg() checks whether the ID registers are final. The test then fails on the first such register: arm64/set_id_regs.c:870: r < 0 && errno == EBUSY ID_DFR0_EL1_PerfMon write after failed first run: r=0 errno=16 KernelCI hits this on every run on an AArch64 only GB300 host. Only a field that userspace can change can be frozen, and KVM reports these registers as not writable in KVM_ARM_GET_REG_WRITABLE_MASKS. Skip the fields that the writable mask does not cover. test_vm_ftr_id_regs() already requires the mask to cover every other field in test_regs, so this only drops the fields KVM never lets userspace change. Whether KVM accepts writes to fields it reports as not writable is a separate question from finalization. Fixes: 00e309933879 ("KVM: arm64: selftests: Check ID regs are immutable after a failed run") Link: https://d.kernelci.org/test/maestro:6adcad0c55fda50760800a00 Signed-off-by: Sasha Levin Reviewed-by: Fuad Tabba Tested-by: Fuad Tabba Link: https://patch.msgid.link/20261026012128.2270251-1-sashal@kernel.org Signed-off-by: Marc Zyngier --- tools/testing/selftests/kvm/arm64/set_id_regs.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/kvm/arm64/set_id_regs.c b/tools/testing/selftests/kvm/arm64/set_id_regs.c index 10849d21c0dd..1d2cc25cb3f4 100644 --- a/tools/testing/selftests/kvm/arm64/set_id_regs.c +++ b/tools/testing/selftests/kvm/arm64/set_id_regs.c @@ -815,6 +815,10 @@ static void test_idreg_frozen_after_failed_run(void) SYS_REVIDR_EL1, SYS_AIDR_EL1, }; + u64 masks[KVM_ARM_FEATURE_ID_RANGE_SIZE]; + struct reg_mask_range range = { + .addr = (__u64)masks, + }; struct kvm_vcpu_init init; struct kvm_vcpu *vcpu; struct kvm_vm *vm; @@ -831,6 +835,7 @@ static void test_idreg_frozen_after_failed_run(void) vm = vm_create(1); vm_enable_cap(vm, KVM_CAP_ARM_WRITABLE_IMP_ID_REGS, 0); + vm_ioctl(vm, KVM_ARM_GET_REG_WRITABLE_MASKS, &range); kvm_get_default_vcpu_target(vm, &init); init.features[0] |= (1 << KVM_ARM_VCPU_PMU_V3); vcpu = aarch64_vcpu_add(vm, 0, &init, guest_code); @@ -852,7 +857,9 @@ static void test_idreg_frozen_after_failed_run(void) */ for (int i = 0; i < ARRAY_SIZE(test_regs); i++) { const struct reg_ftr_bits *ftr_bits = test_regs[i].ftr_bits; - u64 reg = KVM_ARM64_SYS_REG(test_regs[i].reg); + u32 reg_id = test_regs[i].reg; + u64 reg = KVM_ARM64_SYS_REG(reg_id); + u64 mask = masks[encoding_to_range_idx(reg_id)]; u64 val = vcpu_get_reg(vcpu, reg); for (int j = 0; ftr_bits[j].type != FTR_END; j++) { @@ -860,6 +867,10 @@ static void test_idreg_frozen_after_failed_run(void) u64 safe = get_safe_value(&ftr_bits[j], ftr); u64 new_val; + /* Only a field userspace could change can be frozen. */ + if ((mask & ftr_bits[j].mask) != ftr_bits[j].mask) + continue; + if (safe == ftr) continue;