linux-kernel - [PATCH 6.1.y 09/21] KVM: x86: Plumb "force_immediate_exit" into kvm

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Message-ID: <20250815001205.2370711-10-seanjc@google.com>
Date: Thu, 14 Aug 2025 17:11:53 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: stable@...r.kernel.org, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Sasha Levin <sashal@...nel.org>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 6.1.y 09/21] KVM: x86: Plumb "force_immediate_exit" into
 kvm_entry() tracepoint

[ Upstream commit 9c9025ea003a03f967affd690f39b4ef3452c0f5 ]

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>
Link: https://lore.kernel.org/r/20240110012705.506918-2-seanjc@google.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 555c7bf35e28..93f523762854 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1528,7 +1528,8 @@ 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 2c0f9c7d1242..b4283c2358a6 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4005,12 +4005,13 @@ 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 6c1dcf44c4fa..ab407bc00d84 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 390af16d9a67..0b495979a02b 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7171,7 +7171,7 @@ 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;
@@ -7198,7 +7198,7 @@ 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 e7c73360890d..652f90ad7107 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10856,7 +10856,7 @@ 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;
 
-- 
2.51.0.rc1.163.g2494970778-goog