From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1426767AbeCBKz7 (ORCPT ); Fri, 2 Mar 2018 05:55:59 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:37786 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1426720AbeCBKzL (ORCPT ); Fri, 2 Mar 2018 05:55:11 -0500 From: Vitaly Kuznetsov To: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, x86@kernel.org, Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Andy Lutomirski Subject: [PATCH RFC 3/3] x86/kvm/vmx: avoid expensive rdmsr for MSR_GS_BASE Date: Fri, 2 Mar 2018 11:55:03 +0100 Message-Id: <20180302105503.24428-4-vkuznets@redhat.com> In-Reply-To: <20180302105503.24428-1-vkuznets@redhat.com> References: <20180302105503.24428-1-vkuznets@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org vmx_save_host_state() is only called from kvm_arch_vcpu_ioctl_run() so the context is pretty well defined and as we're past 'swapgs' MSR_GS_BASE should contain kernel's GS base which we point to irq_stack_union. irq_stack_union needs to be exported as KVM can be a module. Signed-off-by: Vitaly Kuznetsov --- arch/x86/kernel/cpu/common.c | 1 + arch/x86/kvm/vmx.c | 3 ++- 2 files changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 348cf4821240..057393711093 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1398,6 +1398,7 @@ __setup("clearcpuid=", setup_clearcpuid); #ifdef CONFIG_X86_64 DEFINE_PER_CPU_FIRST(union irq_stack_union, irq_stack_union) __aligned(PAGE_SIZE) __visible; +EXPORT_PER_CPU_SYMBOL(irq_stack_union); /* * The following percpu variables are hot. Align current_task to diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 5be34d13d88f..bf856b7ece3f 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -2158,7 +2158,8 @@ static void vmx_save_host_state(struct kvm_vcpu *vcpu) #ifdef CONFIG_X86_64 vmcs_writel(HOST_FS_BASE, current->thread.fsbase); - vmcs_writel(HOST_GS_BASE, read_msr(MSR_GS_BASE)); + vmcs_writel(HOST_GS_BASE, (unsigned long) + per_cpu(irq_stack_union.gs_base, smp_processor_id())); #else vmcs_writel(HOST_FS_BASE, segment_base(vmx->host_state.fs_sel)); vmcs_writel(HOST_GS_BASE, segment_base(vmx->host_state.gs_sel)); -- 2.14.3