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

From: Sagi Shahar
Date: Thu Jul 25 2024 - 18:36:01 EST

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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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