From: Lorenzo Brescia <lorenzo.brescia@edu.unito.it>
Date: Wed, 23 Dec 2020 14:45:07 +0000
Subject: kvm: tracing: Fix unmatched kvm_entry and kvm_exit events
Git-commit: d95df9510679757bdfc22376d351cdf367b3a604
Patch-mainline: v5.11-rc6
References: bsc#1182770

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>
---
 arch/x86/kvm/svm/svm.c | 2 ++
 arch/x86/kvm/vmx/vmx.c | 2 ++
 arch/x86/kvm/x86.c     | 3 +--
 3 files changed, 5 insertions(+), 2 deletions(-)

--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6608,6 +6608,8 @@
 	if (vmx->emulation_required)
 		return;
 
+	trace_kvm_entry(vcpu);
+
 	if (vmx->ple_window_dirty) {
 		vmx->ple_window_dirty = false;
 		vmcs_write32(PLE_WINDOW, vmx->ple_window);
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8113,7 +8113,6 @@
 		kvm_x86_ops->request_immediate_exit(vcpu);
 	}
 
-	trace_kvm_entry(vcpu->vcpu_id);
 	guest_enter_irqoff();
 
 	fpregs_assert_state_consistent();
@@ -10220,6 +10219,7 @@
 EXPORT_SYMBOL_GPL(kvm_arch_no_poll);
 
 
+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);
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -5665,6 +5665,8 @@
 {
 	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];