KVM: VMX: Move enable_ipiv knob to common x86

Move enable_ipiv to common x86 so that it can be reused by SVM to control
IPI virtualization when AVIC is enabled.  SVM doesn't actually provide a
way to truly disable IPI virtualization, but KVM can get close enough by
skipping the necessary table programming.

Link: https://lore.kernel.org/r/20250611224604.313496-18-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: sean-jc

arch/x86/include/asm/kvm_host.h

@@ -1951,6 +1951,7 @@ struct kvm_arch_async_pf {
 extern u32 __read_mostly kvm_nr_uret_msrs;
 extern bool __read_mostly allow_smaller_maxphyaddr;
 extern bool __read_mostly enable_apicv;
+extern bool __read_mostly enable_ipiv;
 extern bool __read_mostly enable_device_posted_irqs;
 extern struct kvm_x86_ops kvm_x86_ops;
 

arch/x86/kvm/vmx/capabilities.h

@@ -15,7 +15,6 @@ extern bool __read_mostly enable_ept;
 extern bool __read_mostly enable_unrestricted_guest;
 extern bool __read_mostly enable_ept_ad_bits;
 extern bool __read_mostly enable_pml;
-extern bool __read_mostly enable_ipiv;
 extern int __read_mostly pt_mode;
 
 #define PT_MODE_SYSTEM		0

arch/x86/kvm/vmx/vmx.c

@@ -113,8 +113,6 @@ static bool __read_mostly fasteoi = 1;
 module_param(fasteoi, bool, 0444);
 
 module_param(enable_apicv, bool, 0444);
-
-bool __read_mostly enable_ipiv = true;
 module_param(enable_ipiv, bool, 0444);
 
 module_param(enable_device_posted_irqs, bool, 0444);

arch/x86/kvm/x86.c

@@ -226,6 +226,9 @@ EXPORT_SYMBOL_GPL(allow_smaller_maxphyaddr);
 bool __read_mostly enable_apicv = true;
 EXPORT_SYMBOL_GPL(enable_apicv);
 
+bool __read_mostly enable_ipiv = true;
+EXPORT_SYMBOL_GPL(enable_ipiv);
+
 bool __read_mostly enable_device_posted_irqs = true;
 EXPORT_SYMBOL_GPL(enable_device_posted_irqs);