From patchwork Mon Jul 23 19:32:49 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 10540793 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 5C590A517 for ; Mon, 23 Jul 2018 19:33:33 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 49B992832D for ; Mon, 23 Jul 2018 19:33:33 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 3E4B12841C; Mon, 23 Jul 2018 19:33:33 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id DA6F32832D for ; Mon, 23 Jul 2018 19:33:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388127AbeGWUgL (ORCPT ); Mon, 23 Jul 2018 16:36:11 -0400 Received: from mga02.intel.com ([134.134.136.20]:3733 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388111AbeGWUgK (ORCPT ); Mon, 23 Jul 2018 16:36:10 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 23 Jul 2018 12:33:28 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.51,394,1526367600"; d="scan'208";a="247679542" Received: from sjchrist-coffee.jf.intel.com ([10.54.74.132]) by fmsmga005.fm.intel.com with ESMTP; 23 Jul 2018 12:32:55 -0700 From: Sean Christopherson To: kvm@vger.kernel.org, pbonzini@redhat.com, rkrcmar@redhat.com Cc: sean.j.christopherson@intel.com Subject: [PATCH 10/11] KVM: vmx: skip VMWRITE of HOST_{FS,GS}_SEL when possible Date: Mon, 23 Jul 2018 12:32:49 -0700 Message-Id: <20180723193250.13555-11-sean.j.christopherson@intel.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180723193250.13555-1-sean.j.christopherson@intel.com> References: <20180723193250.13555-1-sean.j.christopherson@intel.com> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On a 64-bit host, FS.sel and GS.sel are all but guaranteed to be 0, which in turn means they'll rarely change. Skip the VMWRITE for the associated VMCS fields when loading host state if the selector hasn't changed since the last VMWRITE. Signed-off-by: Sean Christopherson Reviewed-by: Peter Shier Tested-by: Peter Shier --- arch/x86/kvm/vmx.c | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index b24cd74c905c..9f3bd199dc8c 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -2619,16 +2619,20 @@ static void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu) gs_base = segment_base(gs_sel); #endif - host_state->fs_sel = fs_sel; - if (!(fs_sel & 7)) - vmcs_write16(HOST_FS_SELECTOR, fs_sel); - else - vmcs_write16(HOST_FS_SELECTOR, 0); - host_state->gs_sel = gs_sel; - if (!(gs_sel & 7)) - vmcs_write16(HOST_GS_SELECTOR, gs_sel); - else - vmcs_write16(HOST_GS_SELECTOR, 0); + if (unlikely(fs_sel != host_state->fs_sel)) { + if (!(fs_sel & 7)) + vmcs_write16(HOST_FS_SELECTOR, fs_sel); + else + vmcs_write16(HOST_FS_SELECTOR, 0); + host_state->fs_sel = fs_sel; + } + if (unlikely(gs_sel != host_state->gs_sel)) { + if (!(gs_sel & 7)) + vmcs_write16(HOST_GS_SELECTOR, gs_sel); + else + vmcs_write16(HOST_GS_SELECTOR, 0); + host_state->gs_sel = gs_sel; + } vmcs_writel(HOST_FS_BASE, fs_base); vmcs_writel(HOST_GS_BASE, gs_base);