Now that FRED provides C-code entry points for handling IRQ and NMI exits, use the FRED infrastructure for forwarding all such events even if FRED isn't supported in hardware. Avoiding the non-FRED assembly trampolines into the IDT handlers for IRQs eliminates the associated non-CFI indirect call (KVM performs a CALL by doing a lookup on the IDT using the IRQ vector). Force FRED for 64-bit kernels if KVM_INTEL is enabled, as the benefits of eliminating the IRQ trampoline usage far outwieghts the code overhead for FRED. Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> --- arch/x86/kvm/Kconfig | 1 + arch/x86/kvm/vmx/vmx.c | 4 ++-- 2 files changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig index 2eeffcec5382..712a2ff28ce4 100644 --- a/arch/x86/kvm/Kconfig +++ b/arch/x86/kvm/Kconfig @@ -95,6 +95,7 @@ config KVM_SW_PROTECTED_VM config KVM_INTEL tristate "KVM for Intel (and compatible) processors support" depends on KVM && IA32_FEAT_CTL + select X86_FRED if X86_64 select KVM_GENERIC_PRIVATE_MEM if INTEL_TDX_HOST select KVM_GENERIC_MEMORY_ATTRIBUTES if INTEL_TDX_HOST help diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index ef2d7208dd20..2ea89985107d 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6995,7 +6995,7 @@ static void handle_external_interrupt_irqoff(struct kvm_vcpu *vcpu, return; kvm_before_interrupt(vcpu, KVM_HANDLING_IRQ); - if (cpu_feature_enabled(X86_FEATURE_FRED)) + if (IS_ENABLED(CONFIG_X86_FRED)) fred_entry_from_kvm(EVENT_TYPE_EXTINT, vector); else vmx_do_interrupt_irqoff(gate_offset((gate_desc *)host_idt_base + vector)); @@ -7268,7 +7268,7 @@ noinstr void vmx_handle_nmi(struct kvm_vcpu *vcpu) return; kvm_before_interrupt(vcpu, KVM_HANDLING_NMI); - if (cpu_feature_enabled(X86_FEATURE_FRED)) + if (IS_ENABLED(CONFIG_X86_FRED)) fred_entry_from_kvm(EVENT_TYPE_NMI, NMI_VECTOR); else vmx_do_nmi_irqoff(); -- 2.49.0.906.g1f30a19c02-goog
