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: Lorenzo Brescia <lorenzo.brescia@edu.unito.it>
Signed-off-by: Dario Faggioli <dfaggioli@suse.com>
Message-Id: <160873470698.11652.13483635328769030605.stgit@Wayrath>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 7ef171790d02b669ffaa677cf0519972774ea384..f923e14e87df2e12a97af016b2e3c72aa92eac16 100644 (file)
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -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];

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 2af05d3b0590985ce22ee26e6a83b0848b6043ef..cc60b1fc3ee71c7fd81e28a4cc9f7294048ea0b5 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6653,6 +6653,8 @@ reenter_guest:
        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);

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9025c7673af616b70088bb16c3521f1ab2110499..1f64e8b97605d30df21dc6f56bb793ca5f656b4b 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -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);