From patchwork Tue Mar 13 17:48:05 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vitaly Kuznetsov X-Patchwork-Id: 10280309 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 3B3D3601A0 for ; Tue, 13 Mar 2018 17:48:42 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2C2C028950 for ; Tue, 13 Mar 2018 17:48:42 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 20C4A28989; Tue, 13 Mar 2018 17:48:42 +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=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable 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 BF69328950 for ; Tue, 13 Mar 2018 17:48:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932345AbeCMRs0 (ORCPT ); Tue, 13 Mar 2018 13:48:26 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:42114 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751850AbeCMRsM (ORCPT ); Tue, 13 Mar 2018 13:48:12 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D8067E44B5; Tue, 13 Mar 2018 17:48:11 +0000 (UTC) Received: from vitty.brq.redhat.com (unknown [10.43.2.155]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6E210202322A; Tue, 13 Mar 2018 17:48:10 +0000 (UTC) From: Vitaly Kuznetsov To: kvm@vger.kernel.org, x86@kernel.org Cc: linux-kernel@vger.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 v2 2/2] x86/kvm/vmx: avoid expensive rdmsr for MSR_GS_BASE Date: Tue, 13 Mar 2018 18:48:05 +0100 Message-Id: <20180313174805.11825-3-vkuznets@redhat.com> In-Reply-To: <20180313174805.11825-1-vkuznets@redhat.com> References: <20180313174805.11825-1-vkuznets@redhat.com> X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Tue, 13 Mar 2018 17:48:11 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Tue, 13 Mar 2018 17:48:11 +0000 (UTC) for IP:'10.11.54.4' DOMAIN:'int-mx04.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'vkuznets@redhat.com' RCPT:'' Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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. Add new kernelmode_gs_base() API, irq_stack_union needs to be exported as KVM can be build as module. Acked-by: Andy Lutomirski Signed-off-by: Vitaly Kuznetsov --- arch/x86/include/asm/processor.h | 5 +++++ arch/x86/kernel/cpu/common.c | 3 ++- arch/x86/kvm/vmx.c | 3 ++- 3 files changed, 9 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 1d816a3325a1..4fa4206029e3 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -407,6 +407,11 @@ union irq_stack_union { DECLARE_PER_CPU_FIRST(union irq_stack_union, irq_stack_union) __visible; DECLARE_INIT_PER_CPU(irq_stack_union); +static inline unsigned long cpu_kernelmode_gs_base(int cpu) +{ + return (unsigned long)per_cpu(irq_stack_union.gs_base, cpu); +} + DECLARE_PER_CPU(char *, irq_stack_ptr); DECLARE_PER_CPU(unsigned int, irq_count); extern asmlinkage void ignore_sysret(void); diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 348cf4821240..4702fbd98f92 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -487,7 +487,7 @@ void load_percpu_segment(int cpu) loadsegment(fs, __KERNEL_PERCPU); #else __loadsegment_simple(gs, 0); - wrmsrl(MSR_GS_BASE, (unsigned long)per_cpu(irq_stack_union.gs_base, cpu)); + wrmsrl(MSR_GS_BASE, cpu_kernelmode_gs_base(cpu)); #endif load_stack_canary_segment(); } @@ -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_GPL(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 189a347f3952..49953e362e92 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -2123,6 +2123,7 @@ static unsigned long segment_base(u16 selector) static void vmx_save_host_state(struct kvm_vcpu *vcpu) { struct vcpu_vmx *vmx = to_vmx(vcpu); + int cpu = raw_smp_processor_id(); int i; if (vmx->host_state.loaded) @@ -2165,7 +2166,7 @@ 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, cpu_kernelmode_gs_base(cpu)); #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));