From: Avi Kivity <[email protected]> Only reload debug register 6 if we're running with the guest's debug registers. Saves around 150 cycles from the guest lightweight exit path.
dr6 contains a couple of bits that are updated on #DB, so intercept that unconditionally and update those bits then. Signed-off-by: Avi Kivity <[email protected]> Signed-off-by: Marcelo Tosatti <[email protected]> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index bf0d00b..d3213ac 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -539,10 +539,12 @@ static void update_exception_bitmap(struct kvm_vcpu *vcpu) eb = (1u << PF_VECTOR) | (1u << UD_VECTOR) | (1u << MC_VECTOR); if (!vcpu->fpu_active) eb |= 1u << NM_VECTOR; + /* + * Unconditionally intercept #DB so we can maintain dr6 without + * reading it every exit. + */ + eb |= 1u << DB_VECTOR; if (vcpu->guest_debug & KVM_GUESTDBG_ENABLE) { - if (vcpu->guest_debug & - (KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP)) - eb |= 1u << DB_VECTOR; if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP) eb |= 1u << BP_VECTOR; } @@ -3625,7 +3627,8 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu) */ vmcs_writel(HOST_CR0, read_cr0()); - set_debugreg(vcpu->arch.dr6, 6); + if (vcpu->arch.switch_db_regs) + set_debugreg(vcpu->arch.dr6, 6); asm( /* Store host registers */ @@ -3727,7 +3730,8 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu) | (1 << VCPU_EXREG_PDPTR)); vcpu->arch.regs_dirty = 0; - get_debugreg(vcpu->arch.dr6, 6); + if (vcpu->arch.switch_db_regs) + get_debugreg(vcpu->arch.dr6, 6); vmx->idt_vectoring_info = vmcs_read32(IDT_VECTORING_INFO_FIELD); if (vmx->rmode.irq.pending) -- To unsubscribe from this list: send the line "unsubscribe kvm-commits" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
