linux-kernel - [PATCH 1/6] KVM: x86: Plumb "force_immediate_exit" into kvm

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Date: Tue,  9 Jan 2024 17:27:00 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH 1/6] KVM: x86: Plumb "force_immediate_exit" into kvm_entry() tracepoint

Annotate the kvm_entry() tracepoint with "immediate exit" when KVM is
forcing a VM-Exit immediately after VM-Enter, e.g. when KVM wants to
inject an event but needs to first complete some other operation.
Knowing that KVM is (or isn't) forcing an exit is useful information when
debugging issues related to event injection.

Suggested-by: Maxim Levitsky <mlevitsk@...hat.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/include/asm/kvm_host.h | 3 ++-
 arch/x86/kvm/svm/svm.c          | 5 +++--
 arch/x86/kvm/trace.h            | 9 ++++++---
 arch/x86/kvm/vmx/vmx.c          | 4 ++--
 arch/x86/kvm/x86.c              | 2 +-
 5 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 7bc1daf68741..9c90664ef9fb 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1663,7 +1663,8 @@ struct kvm_x86_ops {
 	void (*flush_tlb_guest)(struct kvm_vcpu *vcpu);
 
 	int (*vcpu_pre_run)(struct kvm_vcpu *vcpu);
-	enum exit_fastpath_completion (*vcpu_run)(struct kvm_vcpu *vcpu);
+	enum exit_fastpath_completion (*vcpu_run)(struct kvm_vcpu *vcpu,
+						  bool force_immediate_exit);
 	int (*handle_exit)(struct kvm_vcpu *vcpu,
 		enum exit_fastpath_completion exit_fastpath);
 	int (*skip_emulated_instruction)(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 2171b0cda8d4..f5f3301d2a01 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4115,12 +4115,13 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu, bool spec_ctrl_in
 	guest_state_exit_irqoff();
 }
 
-static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu)
+static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu,
+					  bool force_immediate_exit)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
 	bool spec_ctrl_intercepted = msr_write_intercepted(vcpu, MSR_IA32_SPEC_CTRL);
 
-	trace_kvm_entry(vcpu);
+	trace_kvm_entry(vcpu, force_immediate_exit);
 
 	svm->vmcb->save.rax = vcpu->arch.regs[VCPU_REGS_RAX];
 	svm->vmcb->save.rsp = vcpu->arch.regs[VCPU_REGS_RSP];
diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
index 83843379813e..88659de4d2a7 100644
--- a/arch/x86/kvm/trace.h
+++ b/arch/x86/kvm/trace.h
@@ -15,20 +15,23 @@
  * Tracepoint for guest mode entry.
  */
 TRACE_EVENT(kvm_entry,
-	TP_PROTO(struct kvm_vcpu *vcpu),
-	TP_ARGS(vcpu),
+	TP_PROTO(struct kvm_vcpu *vcpu, bool force_immediate_exit),
+	TP_ARGS(vcpu, force_immediate_exit),
 
 	TP_STRUCT__entry(
 		__field(	unsigned int,	vcpu_id		)
 		__field(	unsigned long,	rip		)
+		__field(	bool,		immediate_exit	)
 	),
 
 	TP_fast_assign(
 		__entry->vcpu_id        = vcpu->vcpu_id;
 		__entry->rip		= kvm_rip_read(vcpu);
+		__entry->immediate_exit	= force_immediate_exit;
 	),
 
-	TP_printk("vcpu %u, rip 0x%lx", __entry->vcpu_id, __entry->rip)
+	TP_printk("vcpu %u, rip 0x%lx%s", __entry->vcpu_id, __entry->rip,
+		  __entry->immediate_exit ? "[immediate exit]" : "")
 );
 
 /*
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index d21f55f323ea..51d0f3985463 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7268,7 +7268,7 @@ static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
 	guest_state_exit_irqoff();
 }
 
-static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
+static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	unsigned long cr3, cr4;
@@ -7295,7 +7295,7 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
 		return EXIT_FASTPATH_NONE;
 	}
 
-	trace_kvm_entry(vcpu);
+	trace_kvm_entry(vcpu, force_immediate_exit);
 
 	if (vmx->ple_window_dirty) {
 		vmx->ple_window_dirty = false;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 27e23714e960..e4523ca3dedf 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10962,7 +10962,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 		WARN_ON_ONCE((kvm_vcpu_apicv_activated(vcpu) != kvm_vcpu_apicv_active(vcpu)) &&
 			     (kvm_get_apic_mode(vcpu) != LAPIC_MODE_DISABLED));
 
-		exit_fastpath = static_call(kvm_x86_vcpu_run)(vcpu);
+		exit_fastpath = static_call(kvm_x86_vcpu_run)(vcpu, req_immediate_exit);
 		if (likely(exit_fastpath != EXIT_FASTPATH_REENTER_GUEST))
 			break;
 
-- 
2.43.0.472.g3155946c3a-goog