From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756536AbaC0Lci (ORCPT ); Thu, 27 Mar 2014 07:32:38 -0400 Received: from mail-ee0-f49.google.com ([74.125.83.49]:51128 "EHLO mail-ee0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751683AbaC0Lar (ORCPT ); Thu, 27 Mar 2014 07:30:47 -0400 From: Paolo Bonzini To: linux-kernel@vger.kernel.org Cc: kvm@vger.kernel.org Subject: [RFC PATCH 1/5] KVM: vmx: speed up emulation of invalid guest state Date: Thu, 27 Mar 2014 12:30:34 +0100 Message-Id: <1395919838-18466-2-git-send-email-pbonzini@redhat.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1395919838-18466-1-git-send-email-pbonzini@redhat.com> References: <1395919838-18466-1-git-send-email-pbonzini@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org About 25% of the time spent in emulation of invalid guest state is wasted in checking whether emulation is required for the next instruction. However, this almost never changes except when a segment register (or TR or LDTR) changes, or when there is a mode transition (i.e. CR0 changes). In fact, vmx_set_segment and vmx_set_cr0 already modify vmx->emulation_required (except that the former for some reason uses |= instead of just an assignment). So there is no need to call guest_state_valid in the emulation loop. Emulation performance test results indicate 530-870 cycles for common instructions, versus 740-1110 before this patch. Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 1320e0f8e611..73aa522db47b 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -3629,7 +3629,7 @@ static void vmx_set_segment(struct kvm_vcpu *vcpu, vmcs_write32(sf->ar_bytes, vmx_segment_access_rights(var)); out: - vmx->emulation_required |= emulation_required(vcpu); + vmx->emulation_required = emulation_required(vcpu); } static void vmx_get_cs_db_l_bits(struct kvm_vcpu *vcpu, int *db, int *l) @@ -5580,7 +5580,7 @@ static int handle_invalid_guest_state(struct kvm_vcpu *vcpu) cpu_exec_ctrl = vmcs_read32(CPU_BASED_VM_EXEC_CONTROL); intr_window_requested = cpu_exec_ctrl & CPU_BASED_VIRTUAL_INTR_PENDING; - while (!guest_state_valid(vcpu) && count-- != 0) { + while (vmx->emulation_required && count-- != 0) { if (intr_window_requested && vmx_interrupt_allowed(vcpu)) return handle_interrupt_window(&vmx->vcpu); @@ -5614,7 +5614,6 @@ static int handle_invalid_guest_state(struct kvm_vcpu *vcpu) schedule(); } - vmx->emulation_required = emulation_required(vcpu); out: return ret; } -- 1.8.3.1