Hi Marc, On Mon, Jul 21, 2025 at 04:51:36PM +0100, Marc Zyngier wrote: > Tinkering with UUIDs is a perilious task, and the KVM UUID gets > broken at times. In order to spot this early enough, add a selftest > that will shout if the expected value isn't found. > > Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx> > Link: https://lore.kernel.org/r/20250721130558.50823-1-jackabt.amazon@xxxxxxxxx > --- > tools/testing/selftests/kvm/Makefile.kvm | 1 + > tools/testing/selftests/kvm/arm64/kvm-uuid.c | 67 ++++++++++++++++++++ > 2 files changed, 68 insertions(+) > create mode 100644 tools/testing/selftests/kvm/arm64/kvm-uuid.c > > diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm > index ce817a975e50a..e1eb1ba238a2a 100644 > --- a/tools/testing/selftests/kvm/Makefile.kvm > +++ b/tools/testing/selftests/kvm/Makefile.kvm > @@ -167,6 +167,7 @@ TEST_GEN_PROGS_arm64 += arm64/vgic_irq > TEST_GEN_PROGS_arm64 += arm64/vgic_lpi_stress > TEST_GEN_PROGS_arm64 += arm64/vpmu_counter_access > TEST_GEN_PROGS_arm64 += arm64/no-vgic-v3 > +TEST_GEN_PROGS_arm64 += arm64/kvm-uuid > TEST_GEN_PROGS_arm64 += access_tracking_perf_test > TEST_GEN_PROGS_arm64 += arch_timer > TEST_GEN_PROGS_arm64 += coalesced_io_test > diff --git a/tools/testing/selftests/kvm/arm64/kvm-uuid.c b/tools/testing/selftests/kvm/arm64/kvm-uuid.c > new file mode 100644 > index 0000000000000..89d9c8b182ae5 > --- /dev/null > +++ b/tools/testing/selftests/kvm/arm64/kvm-uuid.c > @@ -0,0 +1,67 @@ > +#include <errno.h> > +#include <linux/arm-smccc.h> > +#include <asm/kvm.h> > +#include <kvm_util.h> > + > +#include "processor.h" > + > +/* > + * Do NOT redefine these constants, or try to replace them with some > + * "common" version. They are hardcoded here to detect any potential > + * breakage happening in the rest of the kernel. > + * > + * KVM UID value: 28b46fb6-2ec5-11e9-a9ca-4b564d003a74 > + */ > +#define ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_0 0xb66fb428U > +#define ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_1 0xe911c52eU > +#define ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_2 0x564bcaa9U > +#define ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_3 0x743a004dU > + > +static void guest_code(void) > +{ > + struct arm_smccc_res res = {}; > + > + smccc_hvc(ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID, 0, 0, 0, 0, 0, 0, 0, &res); > + > + __GUEST_ASSERT(res.a0 != SMCCC_RET_NOT_SUPPORTED, "a0 = %lx\n", res.a0); Should this check res.a0 == SMCCC_RET_SUCCESS instead? > + __GUEST_ASSERT(res.a0 == ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_0 && > + res.a1 == ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_1 && > + res.a2 == ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_2 && > + res.a3 == ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_3, > + "Unexpected KVM-specific UID %lx %lx %lx %lx\n", res.a0, res.a1, res.a2, res.a3); > + GUEST_DONE(); > +} > + > +int main (int argc, char *argv[]) > +{ > + struct kvm_vcpu *vcpu; > + struct kvm_vm *vm; > + struct ucall uc; > + bool guest_done = false; > + > + vm = vm_create_with_one_vcpu(&vcpu, guest_code); > + > + while (!guest_done) { > + vcpu_run(vcpu); > + > + switch (get_ucall(vcpu, &uc)) { > + case UCALL_SYNC: > + break; > + case UCALL_DONE: > + guest_done = true; > + break; > + case UCALL_ABORT: > + REPORT_GUEST_ASSERT(uc); > + break; > + case UCALL_PRINTF: > + printf("%s", uc.buffer); > + break; > + default: > + TEST_FAIL("Unexpected guest exit"); > + } > + } This is becoming a very common and useful pattern. I wonder if it's time for a ucall helper static void ucall_vcpu_run(struct kvm_vcpu *vcpu, void (*sync_func)(struct kvm_vcpu *, void *), void *sync_data) { bool guest_done = false; struct ucall uc; while (!guest_done) { vcpu_run(vcpu); switch (get_ucall(vcpu, &uc)) { case UCALL_SYNC: if (sync_func) sync_func(vcpu, sync_data); break; case UCALL_DONE: guest_done = true; break; case UCALL_ABORT: REPORT_GUEST_ASSERT(uc); break; case UCALL_PRINTF: printf("%s", uc.buffer); break; default: TEST_FAIL("Unexpected guest exit"); } } } Thanks, drew > + > + kvm_vm_free(vm); > + > + return 0; > +} > -- > 2.39.2 >
