On 07/05/19 21:18, Sean Christopherson wrote: > Pin controls doesn't affect dirty logic, e.g. the preemption timer value > is loaded from vmcs12 even if vmcs12 is "clean", i.e. there is no need > to mark vmcs12 dirty when L1 writes pin controls. > > KVM currently toggles the VMX_PREEMPTION_TIMER control flag when it > disables or enables the timer. The VMWRITE to toggle the flag can be > responsible for a large percentage of vmcs12 dirtying when running KVM > as L1 (depending on the behavior of L2). > > Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx> I think either we wait for patch 13 to get in the wild so that VMX_PREEMPTION_TIMER writes do not become so frequent, or we can do something like --------- 8< ------------ From: Paolo Bonzini <pbonzini@xxxxxxxxxx> Subject: [PATCH] KVM: nVMX: shadow pin based execution controls The VMX_PREEMPTION_TIMER flag may be toggled frequently, though not *very* frequently. Since it does not affect KVM's dirty logic, e.g. the preemption timer value is loaded from vmcs12 even if vmcs12 is "clean", there is no need to mark vmcs12 dirty when L1 writes pin controls, and shadowing the field achieves that. Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> diff --git a/arch/x86/kvm/vmx/vmcs_shadow_fields.h b/arch/x86/kvm/vmx/vmcs_shadow_fields.h index 4cea018ba285..eb1ecd16fd22 100644 --- a/arch/x86/kvm/vmx/vmcs_shadow_fields.h +++ b/arch/x86/kvm/vmx/vmcs_shadow_fields.h @@ -47,6 +47,7 @@ SHADOW_FIELD_RO(GUEST_CS_AR_BYTES, guest_cs_ar_bytes) SHADOW_FIELD_RO(GUEST_SS_AR_BYTES, guest_ss_ar_bytes) SHADOW_FIELD_RW(CPU_BASED_VM_EXEC_CONTROL, cpu_based_vm_exec_control) +SHADOW_FIELD_RW(PIN_BASED_VM_EXEC_CONTROL, pin_based_vm_exec_control) SHADOW_FIELD_RW(EXCEPTION_BITMAP, exception_bitmap) SHADOW_FIELD_RW(VM_ENTRY_EXCEPTION_ERROR_CODE, vm_entry_exception_error_code) SHADOW_FIELD_RW(VM_ENTRY_INTR_INFO_FIELD, vm_entry_intr_info_field)
