Re: [RFC PATCH v5 18/29] KVM: selftests: TDX: Add TDX MMIO writes test

From: Sagi Shahar
Date: Tue Jul 30 2024 - 15:04:07 EST

On Tue, Mar 5, 2024 at 3:28 AM Yan Zhao <yan.y.zhao@xxxxxxxxx> wrote:
>
> On Tue, Dec 12, 2023 at 12:46:33PM -0800, Sagi Shahar wrote:
> > The test verifies MMIO writes of various sizes from the guest to the host.
> >
> > Signed-off-by: Sagi Shahar <sagis@xxxxxxxxxx>
> > Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
> > Signed-off-by: Ryan Afranji <afranji@xxxxxxxxxx>
> > ---
> > .../selftests/kvm/include/x86_64/tdx/tdx.h | 2 +
> > .../selftests/kvm/lib/x86_64/tdx/tdx.c | 14 +++
> > .../selftests/kvm/x86_64/tdx_vm_tests.c | 85 +++++++++++++++++++
> > 3 files changed, 101 insertions(+)
> >
> > diff --git a/tools/testing/selftests/kvm/include/x86_64/tdx/tdx.h b/tools/testing/selftests/kvm/include/x86_64/tdx/tdx.h
> > index 13ce60df5684..502b670ea699 100644
> > --- a/tools/testing/selftests/kvm/include/x86_64/tdx/tdx.h
> > +++ b/tools/testing/selftests/kvm/include/x86_64/tdx/tdx.h
> > @@ -25,5 +25,7 @@ uint64_t tdg_vp_vmcall_instruction_wrmsr(uint64_t index, uint64_t value);
> > uint64_t tdg_vp_vmcall_instruction_hlt(uint64_t interrupt_blocked_flag);
> > uint64_t tdg_vp_vmcall_ve_request_mmio_read(uint64_t address, uint64_t size,
> > uint64_t *data_out);
> > +uint64_t tdg_vp_vmcall_ve_request_mmio_write(uint64_t address, uint64_t size,
> > + uint64_t data_in);
> >
> > #endif // SELFTEST_TDX_TDX_H
> > diff --git a/tools/testing/selftests/kvm/lib/x86_64/tdx/tdx.c b/tools/testing/selftests/kvm/lib/x86_64/tdx/tdx.c
> > index b19f07ebc0e7..f4afa09f7e3d 100644
> > --- a/tools/testing/selftests/kvm/lib/x86_64/tdx/tdx.c
> > +++ b/tools/testing/selftests/kvm/lib/x86_64/tdx/tdx.c
> > @@ -143,3 +143,17 @@ uint64_t tdg_vp_vmcall_ve_request_mmio_read(uint64_t address, uint64_t size,
> >
> > return ret;
> > }
> > +
> > +uint64_t tdg_vp_vmcall_ve_request_mmio_write(uint64_t address, uint64_t size,
> > + uint64_t data_in)
> > +{
> > + struct tdx_hypercall_args args = {
> > + .r11 = TDG_VP_VMCALL_VE_REQUEST_MMIO,
> > + .r12 = size,
> > + .r13 = TDG_VP_VMCALL_VE_REQUEST_MMIO_WRITE,
> > + .r14 = address,
> > + .r15 = data_in,
> > + };
> > +
> > + return __tdx_hypercall(&args, 0);
> > +}
> > diff --git a/tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c b/tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c
> > index 48902b69d13e..5e28ba828a92 100644
> > --- a/tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c
> > +++ b/tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c
> > @@ -885,6 +885,90 @@ void verify_mmio_reads(void)
> > printf("\t ... PASSED\n");
> > }
> >
> > +void guest_mmio_writes(void)
> > +{
> > + uint64_t ret;
> > +
> > + ret = tdg_vp_vmcall_ve_request_mmio_write(TDX_MMIO_TEST_ADDR, 1, 0x12);
> > + if (ret)
> > + tdx_test_fatal(ret);
> > +
> > + ret = tdg_vp_vmcall_ve_request_mmio_write(TDX_MMIO_TEST_ADDR, 2, 0x1234);
> > + if (ret)
> > + tdx_test_fatal(ret);
> > +
> > + ret = tdg_vp_vmcall_ve_request_mmio_write(TDX_MMIO_TEST_ADDR, 4, 0x12345678);
> > + if (ret)
> > + tdx_test_fatal(ret);
> > +
> > + ret = tdg_vp_vmcall_ve_request_mmio_write(TDX_MMIO_TEST_ADDR, 8, 0x1234567890ABCDEF);
> > + if (ret)
> > + tdx_test_fatal(ret);
> > +
> > + // Write across page boundary.
> > + ret = tdg_vp_vmcall_ve_request_mmio_write(PAGE_SIZE - 1, 8, 0);
> > + if (ret)
> > + tdx_test_fatal(ret);
> > +
> > + tdx_test_success();
> > +}
> > +
> > +/*
> > + * Varifies guest MMIO writes.
> > + */
> > +void verify_mmio_writes(void)
> > +{
> > + struct kvm_vm *vm;
> > + struct kvm_vcpu *vcpu;
> > +
> > + uint8_t byte_1;
> > + uint16_t byte_2;
> > + uint32_t byte_4;
> > + uint64_t byte_8;
> > +
> > + vm = td_create();
> > + td_initialize(vm, VM_MEM_SRC_ANONYMOUS, 0);
> > + vcpu = td_vcpu_add(vm, 0, guest_mmio_writes);
> > + td_finalize(vm);
> > +
> > + printf("Verifying TD MMIO writes:\n");
> > +
> > + td_vcpu_run(vcpu);
> > + TDX_TEST_CHECK_GUEST_FAILURE(vcpu);
> > + TDX_TEST_ASSERT_MMIO(vcpu, TDX_MMIO_TEST_ADDR, 1, TDG_VP_VMCALL_VE_REQUEST_MMIO_WRITE);
> > + byte_1 = *(uint8_t *)(vcpu->run->mmio.data);
> > +
> > + td_vcpu_run(vcpu);
> > + TDX_TEST_CHECK_GUEST_FAILURE(vcpu);
> > + TDX_TEST_ASSERT_MMIO(vcpu, TDX_MMIO_TEST_ADDR, 2, TDG_VP_VMCALL_VE_REQUEST_MMIO_WRITE);
> > + byte_2 = *(uint16_t *)(vcpu->run->mmio.data);
> > +
> > + td_vcpu_run(vcpu);
> > + TDX_TEST_CHECK_GUEST_FAILURE(vcpu);
> > + TDX_TEST_ASSERT_MMIO(vcpu, TDX_MMIO_TEST_ADDR, 4, TDG_VP_VMCALL_VE_REQUEST_MMIO_WRITE);
> > + byte_4 = *(uint32_t *)(vcpu->run->mmio.data);
> > +
> > + td_vcpu_run(vcpu);
> > + TDX_TEST_CHECK_GUEST_FAILURE(vcpu);
> > + TDX_TEST_ASSERT_MMIO(vcpu, TDX_MMIO_TEST_ADDR, 8, TDG_VP_VMCALL_VE_REQUEST_MMIO_WRITE);
> > + byte_8 = *(uint64_t *)(vcpu->run->mmio.data);
> > +
> > + TEST_ASSERT_EQ(byte_1, 0x12);
> > + TEST_ASSERT_EQ(byte_2, 0x1234);
> > + TEST_ASSERT_EQ(byte_4, 0x12345678);
> > + TEST_ASSERT_EQ(byte_8, 0x1234567890ABCDEF);
> > +
> > + td_vcpu_run(vcpu);
> > + TEST_ASSERT_EQ(vcpu->run->exit_reason, KVM_EXIT_SYSTEM_EVENT);
> > + TEST_ASSERT_EQ(vcpu->run->system_event.data[1], TDG_VP_VMCALL_INVALID_OPERAND);
> Is it possible that this event is caused by an failure of the last 8 byte write?
> i.e. though MMIO exit to host with correct value 0x1234567890ABCDEF, but guest
> sees ret as TDG_VP_VMCALL_INVALID_OPERAND.
>
> And if, coincidently, guest gets a ret=0 in the next across page boundary write,
> the selftest will show "PASSED", which is not right.
>
We can add another tdx_test_report_to_user_space to synchronize
between guest and host execution making sure that the guest is done
with all the valid writes before testing the negative case.
>
> > + td_vcpu_run(vcpu);
> > + TDX_TEST_ASSERT_SUCCESS(vcpu);
> > +
> > + kvm_vm_free(vm);
> > + printf("\t ... PASSED\n");
> > +}
> > +
> > int main(int argc, char **argv)
> > {
> > setbuf(stdout, NULL);
> > @@ -905,6 +989,7 @@ int main(int argc, char **argv)
> > run_in_new_process(&verify_guest_msr_reads);
> > run_in_new_process(&verify_guest_hlt);
> > run_in_new_process(&verify_mmio_reads);
> > + run_in_new_process(&verify_mmio_writes);
> >
> > return 0;
> > }
> > --
> > 2.43.0.472.g3155946c3a-goog
> >
> >