[RFC PATCH 0/4] TDX KVM selftests

Erdem Aktas
2021-07-26T18:41:24Z

TDX stands for Trust Domain Extensions which isolates VMs from the
virtual-machine manager (VMM)/hypervisor and any other software on the
platform.

Intel has recently submitted a set of RFC patches for KVM support for
TDX and more information can be found on the latest TDX Support
Patches: https://lkml.org/lkml/2021/7/2/558

Due to the nature of the confidential computing environment that TDX
provides, it is very difficult to verify/test the KVM support. TDX
requires UEFI and the guest kernel to be enlightened which are all under
development.

We are working on a set of selftests to close this gap and be able to
verify the KVM functionality to support TDX lifecycle and GHCI [1]
interface.

We are looking for any feedback on:
- Patch series itself
- Any suggestion on how we should approach testing TDX functionality.
Does selftests seems reasonable or should we switch to using KVM
unit tests. I would be happy to get some perspective on how KVM unit
tests can help us more.
- Any test case or scenario that we should add.
- Anything else I have not thought of yet.

Current patch series provide the following capabilities:

- Provide helper functions to create a TD (Trusted Domain) using the KVM
ioctls
- Provide helper functions to create a guest image that can include any
testing code
- Provide helper functions and wrapper functions to write testing code
using GHCI interface
- Add a test case that verifies TDX life cycle
- Add a test case that verifies TDX GHCI port IO

TODOs:
- Use existing function to create page tables dynamically
(ie __virt_pg_map())
- Remove arbitrary defined magic numbers for data structure offsets
- Add TDVMCALL for error reporting
- Add additional test cases as some listed below
- Add #VE handlers to help testing more complicated test cases

Other test cases that we are planning to add:
(with credit to sagis@google.com)

VM call interface Input Output Result
GetTdVmCallInfo R12=0 None VMCALL_SUCCESS
MapGPA Map private page (GPA.S=0) VMCALL_SUCCESS
MapGPA Map shared page (GPA.S=1) VMCALL_SUCCESS
MapGPA Map already private page as private VMCALL_INVALID_OPERAND
MapGPA Map already shared page as shared VMCALL_INVALID_OPERAND
GetQuote
ReportFatalError
SetupEventNotifyInterrupt Valid interrupt value (32:255) VMCALL_SUCCESS
SetupEventNotifyInterrupt Invalid value (>255) VMCALL_INVALID_OPERAND
Instruction.CPUID R12(EAX)=1, R13(ECX)=0 EBX[8:15]=0x8
EBX[16:23]=X
EBX[24:31]=vcpu_id
ECX[0]=1
ECX[12]=Y
Instruction.CPUID R12(EAX)=1, R13(ECX)=4 VMCALL_INVALID_OPERAND
VE.RequestMMIO
Instruction.HLT VMCALL_SUCCESS
Instruction.IO Read/Write 1/2/4 bytes VMCALL_SUCCESS
Instruction.IO Read/Write 3 bytes VMCALL_INVALID_OPERAND
Instruction.RDMSR Accessible register R11=msr_value VMCALL_SUCCESS
Inaccessible register VMCALL_INVALID_OPERAND
Instruction.RDMSR Accessible register VMCALL_SUCCESS
Inaccessible register VMCALL_INVALID_OPERAND
INSTRUCTION.PCONFIG

[1] Intel TDX Guest-Hypervisor Communication Interface
https://software.intel.com/content/dam/develop/external/us/en/documents/intel-tdx-guest-hypervisor-communication-interface.pdf

Erdem Aktas (4):
KVM: selftests: Add support for creating non-default type VMs
KVM: selftest: Add helper functions to create TDX VMs
KVM: selftest: Adding TDX life cycle test.
KVM: selftest: Adding test case for TDX port IO

tools/testing/selftests/kvm/Makefile | 6 +-
.../testing/selftests/kvm/include/kvm_util.h | 1 +
.../selftests/kvm/include/x86_64/processor.h | 5 +
tools/testing/selftests/kvm/lib/kvm_util.c | 29 +-
.../selftests/kvm/lib/x86_64/processor.c | 23 ++
tools/testing/selftests/kvm/lib/x86_64/tdx.h | 220 ++++++++++++
.../selftests/kvm/lib/x86_64/tdx_lib.c | 314 ++++++++++++++++++
.../selftests/kvm/x86_64/tdx_vm_tests.c | 209 ++++++++++++
8 files changed, 800 insertions(+), 7 deletions(-)
create mode 100644 tools/testing/selftests/kvm/lib/x86_64/tdx.h
create mode 100644 tools/testing/selftests/kvm/lib/x86_64/tdx_lib.c
create mode 100644 tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c

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