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Message-ID: <ZeawWs9cAhjLb/YO@yzhao56-desk.sh.intel.com>
Date: Tue, 5 Mar 2024 13:40:42 +0800
From: Yan Zhao <yan.y.zhao@...el.com>
To: Binbin Wu <binbin.wu@...ux.intel.com>
CC: Sagi Shahar <sagis@...gle.com>, <linux-kselftest@...r.kernel.org>,
Ackerley Tng <ackerleytng@...gle.com>, Ryan Afranji <afranji@...gle.com>,
Erdem Aktas <erdemaktas@...gle.com>, Isaku Yamahata
<isaku.yamahata@...el.com>, Sean Christopherson <seanjc@...gle.com>, "Paolo
Bonzini" <pbonzini@...hat.com>, Shuah Khan <shuah@...nel.org>, Peter Gonda
<pgonda@...gle.com>, Haibo Xu <haibo1.xu@...el.com>, Chao Peng
<chao.p.peng@...ux.intel.com>, Vishal Annapurve <vannapurve@...gle.com>,
Roger Wang <runanwang@...gle.com>, Vipin Sharma <vipinsh@...gle.com>,
<jmattson@...gle.com>, <dmatlack@...gle.com>, <linux-kernel@...r.kernel.org>,
<kvm@...r.kernel.org>, <linux-mm@...ck.org>
Subject: Re: [RFC PATCH v5 16/29] KVM: selftests: TDX: Add TDX HLT exit test
On Sat, Mar 02, 2024 at 03:31:07PM +0800, Binbin Wu wrote:
> On 12/13/2023 4:46 AM, Sagi Shahar wrote:
> > The test verifies that the guest runs TDVMCALL<INSTRUCTION.HLT> and the
> > guest vCPU enters to the halted state.
> >
> > Signed-off-by: Erdem Aktas <erdemaktas@...gle.com>
> > Signed-off-by: Sagi Shahar <sagis@...gle.com>
> > Signed-off-by: Ackerley Tng <ackerleytng@...gle.com>
> > Signed-off-by: Ryan Afranji <afranji@...gle.com>
> > ---
> > .../selftests/kvm/include/x86_64/tdx/tdx.h | 2 +
> > .../selftests/kvm/lib/x86_64/tdx/tdx.c | 10 +++
> > .../selftests/kvm/x86_64/tdx_vm_tests.c | 78 +++++++++++++++++++
> > 3 files changed, 90 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 85ba6aab79a7..b18e39d20498 100644
> > --- a/tools/testing/selftests/kvm/include/x86_64/tdx/tdx.h
> > +++ b/tools/testing/selftests/kvm/include/x86_64/tdx/tdx.h
> > @@ -8,6 +8,7 @@
> > #define TDG_VP_VMCALL_GET_TD_VM_CALL_INFO 0x10000
> > #define TDG_VP_VMCALL_REPORT_FATAL_ERROR 0x10003
> > +#define TDG_VP_VMCALL_INSTRUCTION_HLT 12
> > #define TDG_VP_VMCALL_INSTRUCTION_IO 30
> > #define TDG_VP_VMCALL_INSTRUCTION_RDMSR 31
> > #define TDG_VP_VMCALL_INSTRUCTION_WRMSR 32
> > @@ -20,5 +21,6 @@ uint64_t tdg_vp_vmcall_get_td_vmcall_info(uint64_t *r11, uint64_t *r12,
> > uint64_t *r13, uint64_t *r14);
> > uint64_t tdg_vp_vmcall_instruction_rdmsr(uint64_t index, uint64_t *ret_value);
> > 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);
> > #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 88ea6f2a6469..9485bafedc38 100644
> > --- a/tools/testing/selftests/kvm/lib/x86_64/tdx/tdx.c
> > +++ b/tools/testing/selftests/kvm/lib/x86_64/tdx/tdx.c
> > @@ -114,3 +114,13 @@ uint64_t tdg_vp_vmcall_instruction_wrmsr(uint64_t index, uint64_t value)
> > return __tdx_hypercall(&args, 0);
> > }
> > +
> > +uint64_t tdg_vp_vmcall_instruction_hlt(uint64_t interrupt_blocked_flag)
> > +{
> > + struct tdx_hypercall_args args = {
> > + .r11 = TDG_VP_VMCALL_INSTRUCTION_HLT,
> > + .r12 = interrupt_blocked_flag,
> > + };
> > +
> > + 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 5db3701cc6d9..5fae4c6e5f95 100644
> > --- a/tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c
> > +++ b/tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c
> > @@ -721,6 +721,83 @@ void verify_guest_msr_writes(void)
> > printf("\t ... PASSED\n");
> > }
> > +/*
> > + * Verifies HLT functionality.
> > + */
> > +void guest_hlt(void)
> > +{
> > + uint64_t ret;
> > + uint64_t interrupt_blocked_flag;
> > +
> > + interrupt_blocked_flag = 0;
> > + ret = tdg_vp_vmcall_instruction_hlt(interrupt_blocked_flag);
> > + if (ret)
> > + tdx_test_fatal(ret);
> > +
> > + tdx_test_success();
> > +}
> > +
> > +void _verify_guest_hlt(int signum);
> > +
> > +void wake_me(int interval)
> > +{
> > + struct sigaction action;
> > +
> > + action.sa_handler = _verify_guest_hlt;
> > + sigemptyset(&action.sa_mask);
> > + action.sa_flags = 0;
> > +
> > + TEST_ASSERT(sigaction(SIGALRM, &action, NULL) == 0,
> > + "Could not set the alarm handler!");
> > +
> > + alarm(interval);
> > +}
> > +
> > +void _verify_guest_hlt(int signum)
> > +{
> > + struct kvm_vm *vm;
> > + static struct kvm_vcpu *vcpu;
> > +
> > + /*
> > + * This function will also be called by SIGALRM handler to check the
> > + * vCPU MP State. If vm has been initialized, then we are in the signal
> > + * handler. Check the MP state and let the guest run again.
> > + */
> > + if (vcpu != NULL) {
>
> What if the following case if there is a bug in KVM so that:
>
> In guest, execution of tdg_vp_vmcall_instruction_hlt() return 0, but the
> vcpu is not actually halted. Then guest will call tdx_test_success().
>
> And the first call of _verify_guest_hlt() will call kvm_vm_free(vm) to free
> the vm, which also frees the vcpu, and 1 second later, in this path vcpu
> will
> be accessed after free.
>
Right. Another possibility is that if buggy KVM returns success to guest
without putting guest to halted state, the selftest will still print
"PASSED" because the second _verify_guest_hlt() (after waiting for 1s)
has no chance to get executed before the process exits.
> > + struct kvm_mp_state mp_state;
> > +
> > + vcpu_mp_state_get(vcpu, &mp_state);
> > + TEST_ASSERT_EQ(mp_state.mp_state, KVM_MP_STATE_HALTED);
> > +
> > + /* Let the guest to run and finish the test.*/
> > + mp_state.mp_state = KVM_MP_STATE_RUNNABLE;
> > + vcpu_mp_state_set(vcpu, &mp_state);
> > + return;
> > + }
> > +
> > + vm = td_create();
> > + td_initialize(vm, VM_MEM_SRC_ANONYMOUS, 0);
> > + vcpu = td_vcpu_add(vm, 0, guest_hlt);
> > + td_finalize(vm);
> > +
> > + printf("Verifying HLT:\n");
> > +
> > + printf("\t ... Running guest\n");
> > +
> > + /* Wait 1 second for guest to execute HLT */
> > + wake_me(1);
> > + td_vcpu_run(vcpu);
> > +
> > + TDX_TEST_ASSERT_SUCCESS(vcpu);
> > +
> > + kvm_vm_free(vm);
> > + printf("\t ... PASSED\n");
> > +}
> > +
> > +void verify_guest_hlt(void)
> > +{
> > + _verify_guest_hlt(0);
> > +}
> > int main(int argc, char **argv)
> > {
> > @@ -740,6 +817,7 @@ int main(int argc, char **argv)
> > run_in_new_process(&verify_guest_reads);
> > run_in_new_process(&verify_guest_msr_writes);
> > run_in_new_process(&verify_guest_msr_reads);
> > + run_in_new_process(&verify_guest_hlt);
> > return 0;
> > }
>
>
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