KVM: x86: Convert vcpu_run()'s immediate exit param into a generic bitmap

Convert kvm_x86_ops.vcpu_run()'s "force_immediate_exit" boolean parameter
into an a generic bitmap so that similar "take action" information can be
passed to vendor code without creating a pile of boolean parameters.

This will allow dropping kvm_x86_ops.set_dr6() in favor of a new flag, and
will also allow for adding similar functionality for re-loading debugctl
in the active VMCS.

Opportunistically massage the TDX WARN and comment to prepare for adding
more run_flags, all of which are expected to be mutually exclusive with
TDX, i.e. should be WARNed on.

No functional change intended.

Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250610232010.162191-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: sean-jc

arch/x86/include/asm/kvm_host.h

@@ -1674,6 +1674,10 @@ static inline u16 kvm_lapic_irq_dest_mode(bool dest_mode_logical)
 	return dest_mode_logical ? APIC_DEST_LOGICAL : APIC_DEST_PHYSICAL;
 }
 
+enum kvm_x86_run_flags {
+	KVM_RUN_FORCE_IMMEDIATE_EXIT	= BIT(0),
+};
+
 struct kvm_x86_ops {
 	const char *name;
 
@@ -1755,7 +1759,7 @@ struct kvm_x86_ops {
 
 	int (*vcpu_pre_run)(struct kvm_vcpu *vcpu);
 	enum exit_fastpath_completion (*vcpu_run)(struct kvm_vcpu *vcpu,
-						  bool force_immediate_exit);
+						  u64 run_flags);
 	int (*handle_exit)(struct kvm_vcpu *vcpu,
 		enum exit_fastpath_completion exit_fastpath);
 	int (*skip_emulated_instruction)(struct kvm_vcpu *vcpu);

arch/x86/kvm/svm/svm.c

@@ -4389,9 +4389,9 @@ 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,
-					  bool force_immediate_exit)
+static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu, u64 run_flags)
 {
+	bool force_immediate_exit = run_flags & KVM_RUN_FORCE_IMMEDIATE_EXIT;
 	struct vcpu_svm *svm = to_svm(vcpu);
 	bool spec_ctrl_intercepted = msr_write_intercepted(vcpu, MSR_IA32_SPEC_CTRL);
 

arch/x86/kvm/vmx/main.c

@@ -175,12 +175,12 @@ static int vt_vcpu_pre_run(struct kvm_vcpu *vcpu)
 	return vmx_vcpu_pre_run(vcpu);
 }
 
-static fastpath_t vt_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit)
+static fastpath_t vt_vcpu_run(struct kvm_vcpu *vcpu, u64 run_flags)
 {
 	if (is_td_vcpu(vcpu))
-		return tdx_vcpu_run(vcpu, force_immediate_exit);
+		return tdx_vcpu_run(vcpu, run_flags);
 
-	return vmx_vcpu_run(vcpu, force_immediate_exit);
+	return vmx_vcpu_run(vcpu, run_flags);
 }
 
 static int vt_handle_exit(struct kvm_vcpu *vcpu,

arch/x86/kvm/vmx/tdx.c

@@ -1025,20 +1025,20 @@ static void tdx_load_host_xsave_state(struct kvm_vcpu *vcpu)
 				DEBUGCTLMSR_FREEZE_PERFMON_ON_PMI | \
 				DEBUGCTLMSR_FREEZE_IN_SMM)
 
-fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit)
+fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu, u64 run_flags)
 {
 	struct vcpu_tdx *tdx = to_tdx(vcpu);
 	struct vcpu_vt *vt = to_vt(vcpu);
 
 	/*
-	 * force_immediate_exit requires vCPU entering for events injection with
-	 * an immediately exit followed. But The TDX module doesn't guarantee
-	 * entry, it's already possible for KVM to _think_ it completely entry
-	 * to the guest without actually having done so.
-	 * Since KVM never needs to force an immediate exit for TDX, and can't
-	 * do direct injection, just warn on force_immediate_exit.
+	 * WARN if KVM wants to force an immediate exit, as the TDX module does
+	 * not guarantee entry into the guest, i.e. it's possible for KVM to
+	 * _think_ it completed entry to the guest and forced an immediate exit
+	 * without actually having done so.  Luckily, KVM never needs to force
+	 * an immediate exit for TDX (KVM can't do direct event injection, so
+	 * just WARN and continue on.
 	 */
-	WARN_ON_ONCE(force_immediate_exit);
+	WARN_ON_ONCE(run_flags);
 
 	/*
 	 * Wait until retry of SEPT-zap-related SEAMCALL completes before
@@ -1048,7 +1048,7 @@ fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit)
 	if (unlikely(READ_ONCE(to_kvm_tdx(vcpu->kvm)->wait_for_sept_zap)))
 		return EXIT_FASTPATH_EXIT_HANDLED;
 
-	trace_kvm_entry(vcpu, force_immediate_exit);
+	trace_kvm_entry(vcpu, run_flags & KVM_RUN_FORCE_IMMEDIATE_EXIT);
 
 	if (pi_test_on(&vt->pi_desc)) {
 		apic->send_IPI_self(POSTED_INTR_VECTOR);

arch/x86/kvm/vmx/vmx.c

@@ -7323,8 +7323,9 @@ static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
 	guest_state_exit_irqoff();
 }
 
-fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit)
+fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu, u64 run_flags)
 {
+	bool force_immediate_exit = run_flags & KVM_RUN_FORCE_IMMEDIATE_EXIT;
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	unsigned long cr3, cr4;
 

arch/x86/kvm/vmx/x86_ops.h

@@ -21,7 +21,7 @@ void vmx_vm_destroy(struct kvm *kvm);
 int vmx_vcpu_precreate(struct kvm *kvm);
 int vmx_vcpu_create(struct kvm_vcpu *vcpu);
 int vmx_vcpu_pre_run(struct kvm_vcpu *vcpu);
-fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit);
+fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu, u64 run_flags);
 void vmx_vcpu_free(struct kvm_vcpu *vcpu);
 void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event);
 void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu);
@@ -133,7 +133,7 @@ void tdx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event);
 void tdx_vcpu_free(struct kvm_vcpu *vcpu);
 void tdx_vcpu_load(struct kvm_vcpu *vcpu, int cpu);
 int tdx_vcpu_pre_run(struct kvm_vcpu *vcpu);
-fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit);
+fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu, u64 run_flags);
 void tdx_prepare_switch_to_guest(struct kvm_vcpu *vcpu);
 void tdx_vcpu_put(struct kvm_vcpu *vcpu);
 bool tdx_protected_apic_has_interrupt(struct kvm_vcpu *vcpu);

arch/x86/kvm/x86.c

@@ -10779,6 +10779,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 		dm_request_for_irq_injection(vcpu) &&
 		kvm_cpu_accept_dm_intr(vcpu);
 	fastpath_t exit_fastpath;
+	u64 run_flags;
 
 	bool req_immediate_exit = false;
 
@@ -11023,8 +11024,11 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 		goto cancel_injection;
 	}
 
-	if (req_immediate_exit)
+	run_flags = 0;
+	if (req_immediate_exit) {
+		run_flags |= KVM_RUN_FORCE_IMMEDIATE_EXIT;
 		kvm_make_request(KVM_REQ_EVENT, vcpu);
+	}
 
 	fpregs_assert_state_consistent();
 	if (test_thread_flag(TIF_NEED_FPU_LOAD))
@@ -11061,8 +11065,7 @@ 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 = kvm_x86_call(vcpu_run)(vcpu,
-						       req_immediate_exit);
+		exit_fastpath = kvm_x86_call(vcpu_run)(vcpu, run_flags);
 		if (likely(exit_fastpath != EXIT_FASTPATH_REENTER_GUEST))
 			break;
 
@@ -11074,6 +11077,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 			break;
 		}
 
+		run_flags = 0;
+
 		/* Note, VM-Exits that go down the "slow" path are accounted below. */
 		++vcpu->stat.exits;
 	}