Commit d95df951 authored by Lorenzo Brescia's avatar Lorenzo Brescia Committed by Paolo Bonzini
Browse files

kvm: tracing: Fix unmatched kvm_entry and kvm_exit events 



On VMX, if we exit and then re-enter immediately without leaving
the vmx_vcpu_run() function, the kvm_entry event is not logged.
That means we will see one (or more) kvm_exit, without its (their)
corresponding kvm_entry, as shown here:

 CPU-1979 [002] 89.871187: kvm_entry: vcpu 1
 CPU-1979 [002] 89.871218: kvm_exit:  reason MSR_WRITE
 CPU-1979 [002] 89.871259: kvm_exit:  reason MSR_WRITE

It also seems possible for a kvm_entry event to be logged, but then
we leave vmx_vcpu_run() right away (if vmx->emulation_required is
true). In this case, we will have a spurious kvm_entry event in the
trace.

Fix these situations by moving trace_kvm_entry() inside vmx_vcpu_run()
(where trace_kvm_exit() already is).

A trace obtained with this patch applied looks like this:

 CPU-14295 [000] 8388.395387: kvm_entry: vcpu 0
 CPU-14295 [000] 8388.395392: kvm_exit:  reason MSR_WRITE
 CPU-14295 [000] 8388.395393: kvm_entry: vcpu 0
 CPU-14295 [000] 8388.395503: kvm_exit:  reason EXTERNAL_INTERRUPT

Of course, not calling trace_kvm_entry() in common x86 code any
longer means that we need to adjust the SVM side of things too.

Signed-off-by: default avatarLorenzo Brescia <lorenzo.brescia@edu.unito.it>
Signed-off-by: default avatarDario Faggioli <dfaggioli@suse.com>
Message-Id: <160873470698.11652.13483635328769030605.stgit@Wayrath>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 01ead84c

arch/x86/kvm/svm/svm.c

+2 −0
Original line number Diff line number Diff line
@@ -3739,6 +3739,8 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu) 
{

	struct vcpu_svm *svm = to_svm(vcpu);



	trace_kvm_entry(vcpu);



	svm->vmcb->save.rax = vcpu->arch.regs[VCPU_REGS_RAX];

	svm->vmcb->save.rsp = vcpu->arch.regs[VCPU_REGS_RSP];

	svm->vmcb->save.rip = vcpu->arch.regs[VCPU_REGS_RIP];

arch/x86/kvm/vmx/vmx.c

+2 −0
Original line number Diff line number Diff line
@@ -6653,6 +6653,8 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu) 
	if (vmx->emulation_required)

		return EXIT_FASTPATH_NONE;



	trace_kvm_entry(vcpu);



	if (vmx->ple_window_dirty) {

		vmx->ple_window_dirty = false;

		vmcs_write32(PLE_WINDOW, vmx->ple_window);

arch/x86/kvm/x86.c

+1 −2
Original line number Diff line number Diff line
@@ -8992,8 +8992,6 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) 
		kvm_x86_ops.request_immediate_exit(vcpu);

	}



	trace_kvm_entry(vcpu);



	fpregs_assert_state_consistent();

	if (test_thread_flag(TIF_NEED_FPU_LOAD))

		switch_fpu_return();
@@ -11560,6 +11558,7 @@ int kvm_sev_es_string_io(struct kvm_vcpu *vcpu, unsigned int size, 
}

EXPORT_SYMBOL_GPL(kvm_sev_es_string_io);



EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_entry);

EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_exit);

EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_fast_mmio);

EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_inj_virq);