Re: [RFC PATCH v5 10/29] KVM: selftests: TDX: Adding test case for TDX port IO

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On Sun, Mar 3, 2024 at 8:49 PM Yan Zhao <yan.y.zhao@xxxxxxxxx> wrote:
>
> On Tue, Dec 12, 2023 at 12:46:25PM -0800, Sagi Shahar wrote:
> > From: Erdem Aktas <erdemaktas@xxxxxxxxxx>
> >
> > Verifies TDVMCALL<INSTRUCTION.IO> READ and WRITE operations.
> >
> > Signed-off-by: Erdem Aktas <erdemaktas@xxxxxxxxxx>
> > Signed-off-by: Sagi Shahar <sagis@xxxxxxxxxx>
> > Signed-off-by: Ackerley Tng <ackerleytng@xxxxxxxxxx>
> > Signed-off-by: Ryan Afranji <afranji@xxxxxxxxxx>
> > ---
> >  .../kvm/include/x86_64/tdx/test_util.h        | 34 ++++++++
> >  .../selftests/kvm/x86_64/tdx_vm_tests.c       | 82 +++++++++++++++++++
> >  2 files changed, 116 insertions(+)
> >
> > diff --git a/tools/testing/selftests/kvm/include/x86_64/tdx/test_util.h b/tools/testing/selftests/kvm/include/x86_64/tdx/test_util.h
> > index 6d69921136bd..95a5d5be7f0b 100644
> > --- a/tools/testing/selftests/kvm/include/x86_64/tdx/test_util.h
> > +++ b/tools/testing/selftests/kvm/include/x86_64/tdx/test_util.h
> > @@ -9,6 +9,40 @@
> >  #define TDX_TEST_SUCCESS_PORT 0x30
> >  #define TDX_TEST_SUCCESS_SIZE 4
> >
> > +/**
> > + * Assert that some IO operation involving tdg_vp_vmcall_instruction_io() was
> > + * called in the guest.
> > + */
> > +#define TDX_TEST_ASSERT_IO(VCPU, PORT, SIZE, DIR)                    \
> > +     do {                                                            \
> > +             TEST_ASSERT((VCPU)->run->exit_reason == KVM_EXIT_IO,    \
> > +                     "Got exit_reason other than KVM_EXIT_IO: %u (%s)\n", \
> > +                     (VCPU)->run->exit_reason,                       \
> > +                     exit_reason_str((VCPU)->run->exit_reason));     \
> > +                                                                     \
> > +             TEST_ASSERT(((VCPU)->run->exit_reason == KVM_EXIT_IO) && \
> > +                     ((VCPU)->run->io.port == (PORT)) &&             \
> > +                     ((VCPU)->run->io.size == (SIZE)) &&             \
> > +                     ((VCPU)->run->io.direction == (DIR)),           \
> > +                     "Got unexpected IO exit values: %u (%s) %d %d %d\n", \
> > +                     (VCPU)->run->exit_reason,                       \
> > +                     exit_reason_str((VCPU)->run->exit_reason),      \
> > +                     (VCPU)->run->io.port, (VCPU)->run->io.size,     \
> > +                     (VCPU)->run->io.direction);                     \
> > +     } while (0)
> > +
> > +/**
> > + * Check and report if there was some failure in the guest, either an exception
> > + * like a triple fault, or if a tdx_test_fatal() was hit.
> > + */
> > +#define TDX_TEST_CHECK_GUEST_FAILURE(VCPU)                           \
> > +     do {                                                            \
> > +             if ((VCPU)->run->exit_reason == KVM_EXIT_SYSTEM_EVENT)  \
> > +                     TEST_FAIL("Guest reported error. error code: %lld (0x%llx)\n", \
> > +                             (VCPU)->run->system_event.data[1],      \
> > +                             (VCPU)->run->system_event.data[1]);     \
> > +     } while (0)
> > +
> >  /**
> >   * Assert that tdx_test_success() was called in the guest.
> >   */
> > 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 8638c7bbedaa..75467c407ca7 100644
> > --- a/tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c
> > +++ b/tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c
> > @@ -2,6 +2,7 @@
> >
> >  #include <signal.h>
> >  #include "kvm_util_base.h"
> > +#include "tdx/tdcall.h"
> >  #include "tdx/tdx.h"
> >  #include "tdx/tdx_util.h"
> >  #include "tdx/test_util.h"
> > @@ -74,6 +75,86 @@ void verify_report_fatal_error(void)
> >       printf("\t ... PASSED\n");
> >  }
> >
> > +#define TDX_IOEXIT_TEST_PORT 0x50
> > +
> > +/*
> > + * Verifies IO functionality by writing a |value| to a predefined port.
> > + * Verifies that the read value is |value| + 1 from the same port.
> > + * If all the tests are passed then write a value to port TDX_TEST_PORT
> > + */
> > +void guest_ioexit(void)
> > +{
> > +     uint64_t data_out, data_in, delta;
> > +     uint64_t ret;
> > +
> > +     data_out = 0xAB;
> > +     ret = tdg_vp_vmcall_instruction_io(TDX_IOEXIT_TEST_PORT, 1,
> > +                                     TDG_VP_VMCALL_INSTRUCTION_IO_WRITE,
> > +                                     &data_out);
> > +     if (ret)
> > +             tdx_test_fatal(ret);
> > +
> > +     ret = tdg_vp_vmcall_instruction_io(TDX_IOEXIT_TEST_PORT, 1,
> > +                                     TDG_VP_VMCALL_INSTRUCTION_IO_READ,
> > +                                     &data_in);
> > +     if (ret)
> > +             tdx_test_fatal(ret);
> > +
> > +     delta = data_in - data_out;
> > +     if (delta != 1)
> > +             tdx_test_fatal(ret);
> > +
> > +     tdx_test_success();
> > +}
> > +
> > +void verify_td_ioexit(void)
> > +{
> > +     struct kvm_vm *vm;
> > +     struct kvm_vcpu *vcpu;
> > +
> > +     uint32_t port_data;
> > +
> > +     vm = td_create();
> > +     td_initialize(vm, VM_MEM_SRC_ANONYMOUS, 0);
> > +     vcpu = td_vcpu_add(vm, 0, guest_ioexit);
> > +     td_finalize(vm);
> > +
> > +     printf("Verifying TD IO Exit:\n");
> > +
> > +     /* Wait for guest to do a IO write */
> > +     td_vcpu_run(vcpu);
> > +     TDX_TEST_CHECK_GUEST_FAILURE(vcpu);
> This check is a vain, because the first VMExit from vcpu run is always
> KVM_EXIT_IO caused by tdg_vp_vmcall_instruction_io().
>
>
> > +     TDX_TEST_ASSERT_IO(vcpu, TDX_IOEXIT_TEST_PORT, 1,
> > +                     TDG_VP_VMCALL_INSTRUCTION_IO_WRITE);
> > +     port_data = *(uint8_t *)((void *)vcpu->run + vcpu->run->io.data_offset);
> > +
> > +     printf("\t ... IO WRITE: OK\n");
> So,  even if there's an error in emulating writing of TDX_IOEXIT_TEST_PORT,
> and guest would then find a failure and trigger tdx_test_fatal(), this line
> will still print "IO WRITE: OK", which is not right.

Changed this to "IO WRITE: DONE". This is a useful for understanding
errors if they happen so I don't want to remove this log entirely.
>
> > +
> > +     /*
> > +      * Wait for the guest to do a IO read. Provide the previous written data
> > +      * + 1 back to the guest
> > +      */
> > +     td_vcpu_run(vcpu);
> > +     TDX_TEST_CHECK_GUEST_FAILURE(vcpu);
> This check is a vain, too, as in  write case.

There's no harm in adding this check and it helps debugging issues if
something unexpected happens.
Since this check always come together with td_vcpu_run I'm going to
simplify the code and introduce a TDX_RUN macro that simply runs the
CPU and checks for reported guest failures which is going to replace
the td_vcpu_run/TDX_TEST_CHECK_GUEST_FAILURE combo.
>
> > +     TDX_TEST_ASSERT_IO(vcpu, TDX_IOEXIT_TEST_PORT, 1,
> > +                     TDG_VP_VMCALL_INSTRUCTION_IO_READ);
> > +     *(uint8_t *)((void *)vcpu->run + vcpu->run->io.data_offset) = port_data + 1;
> > +
> > +     printf("\t ... IO READ: OK\n");
> Same as in write case, this line should not be printed until after guest
> finishing checking return code.
>
> > +
> > +     /*
> > +      * Wait for the guest to complete execution successfully. The read
> > +      * value is checked within the guest.
> > +      */
> > +     td_vcpu_run(vcpu);
> > +     TDX_TEST_CHECK_GUEST_FAILURE(vcpu);
> > +     TDX_TEST_ASSERT_SUCCESS(vcpu);
> > +
> > +     printf("\t ... IO verify read/write values: OK\n");
> > +     kvm_vm_free(vm);
> > +     printf("\t ... PASSED\n");
> > +}
> > +
> >  int main(int argc, char **argv)
> >  {
> >       setbuf(stdout, NULL);
> > @@ -85,6 +166,7 @@ int main(int argc, char **argv)
> >
> >       run_in_new_process(&verify_td_lifecycle);
> >       run_in_new_process(&verify_report_fatal_error);
> > +     run_in_new_process(&verify_td_ioexit);
> >
> >       return 0;
> >  }
> > --
> > 2.43.0.472.g3155946c3a-goog
> >
> >
>





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