From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932849Ab0BPKh0 (ORCPT ); Tue, 16 Feb 2010 05:37:26 -0500 Received: from mx1.redhat.com ([209.132.183.28]:59022 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932826Ab0BPKfl (ORCPT ); Tue, 16 Feb 2010 05:35:41 -0500 From: Avi Kivity To: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org Subject: [PATCH 38/38] KVM: Remove redundant reading of rax on OUT instructions Date: Tue, 16 Feb 2010 12:35:36 +0200 Message-Id: <1266316536-28936-39-git-send-email-avi@redhat.com> In-Reply-To: <1266316536-28936-1-git-send-email-avi@redhat.com> References: <1266316536-28936-1-git-send-email-avi@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Takuya Yoshikawa kvm_emulate_pio() and complete_pio() both read out the RAX register value and copy it to a place into which the value read out from the port will be copied later. This patch removes this redundancy. /*** snippet from arch/x86/kvm/x86.c ***/ int complete_pio(struct kvm_vcpu *vcpu) { ... if (!io->string) { if (io->in) { val = kvm_register_read(vcpu, VCPU_REGS_RAX); memcpy(&val, vcpu->arch.pio_data, io->size); kvm_register_write(vcpu, VCPU_REGS_RAX, val); } ... Signed-off-by: Takuya Yoshikawa Signed-off-by: Avi Kivity --- arch/x86/kvm/x86.c | 6 ++++-- 1 files changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index c91007f..bd3161c 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3551,8 +3551,10 @@ int kvm_emulate_pio(struct kvm_vcpu *vcpu, int in, int size, unsigned port) trace_kvm_pio(vcpu->run->io.direction == KVM_EXIT_IO_OUT, port, size, 1); - val = kvm_register_read(vcpu, VCPU_REGS_RAX); - memcpy(vcpu->arch.pio_data, &val, 4); + if (!vcpu->arch.pio.in) { + val = kvm_register_read(vcpu, VCPU_REGS_RAX); + memcpy(vcpu->arch.pio_data, &val, 4); + } if (!kernel_pio(vcpu, vcpu->arch.pio_data)) { complete_pio(vcpu); -- 1.6.5.3