From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1E363C4707F for ; Thu, 27 May 2021 15:14:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E2FD760724 for ; Thu, 27 May 2021 15:14:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237128AbhE0PQQ (ORCPT ); Thu, 27 May 2021 11:16:16 -0400 Received: from mail.kernel.org ([198.145.29.99]:44260 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237098AbhE0PPX (ORCPT ); Thu, 27 May 2021 11:15:23 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 15DF2613C3; Thu, 27 May 2021 15:13:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1622128429; bh=Vy6Ay5huBFbu3BsnKhjEQJUVr1drvFyUZJiC8Kzri3E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=o9qqhFIIdLWCSF6HauAXfEpwMLQeO672UJMvC+ooE+UBskdCRJDBB1z7Q2XN90Xus 0piNlJh2JleQ69hZ7OMk15fAKkt1i/0Yzox74n2Jcb7NWKIaUT1beujFw7ZHNjQRnC 6MJSDi7yUUWFpqxe1LSoAZMp9I+BW6e/3xsR5Tyk= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Thomas Gleixner , Wanpeng Li , Sean Christopherson Subject: [PATCH 5.12 6/7] KVM: x86: Defer vtime accounting til after IRQ handling Date: Thu, 27 May 2021 17:13:07 +0200 Message-Id: <20210527151139.442692176@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210527151139.241267495@linuxfoundation.org> References: <20210527151139.241267495@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Wanpeng Li commit 160457140187c5fb127b844e5a85f87f00a01b14 upstream. Defer the call to account guest time until after servicing any IRQ(s) that happened in the guest or immediately after VM-Exit. Tick-based accounting of vCPU time relies on PF_VCPU being set when the tick IRQ handler runs, and IRQs are blocked throughout the main sequence of vcpu_enter_guest(), including the call into vendor code to actually enter and exit the guest. This fixes a bug where reported guest time remains '0', even when running an infinite loop in the guest: https://bugzilla.kernel.org/show_bug.cgi?id=209831 Fixes: 87fa7f3e98a131 ("x86/kvm: Move context tracking where it belongs") Suggested-by: Thomas Gleixner Co-developed-by: Sean Christopherson Signed-off-by: Wanpeng Li Signed-off-by: Sean Christopherson Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20210505002735.1684165-4-seanjc@google.com Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/svm/svm.c | 6 +++--- arch/x86/kvm/vmx/vmx.c | 6 +++--- arch/x86/kvm/x86.c | 9 +++++++++ 3 files changed, 15 insertions(+), 6 deletions(-) --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -3815,15 +3815,15 @@ static noinstr void svm_vcpu_enter_exit( * have them in state 'on' as recorded before entering guest mode. * Same as enter_from_user_mode(). * - * guest_exit_irqoff() restores host context and reinstates RCU if - * enabled and required. + * context_tracking_guest_exit() restores host context and reinstates + * RCU if enabled and required. * * This needs to be done before the below as native_read_msr() * contains a tracepoint and x86_spec_ctrl_restore_host() calls * into world and some more. */ lockdep_hardirqs_off(CALLER_ADDR0); - guest_exit_irqoff(); + context_tracking_guest_exit(); instrumentation_begin(); trace_hardirqs_off_finish(); --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6701,15 +6701,15 @@ static noinstr void vmx_vcpu_enter_exit( * have them in state 'on' as recorded before entering guest mode. * Same as enter_from_user_mode(). * - * guest_exit_irqoff() restores host context and reinstates RCU if - * enabled and required. + * context_tracking_guest_exit() restores host context and reinstates + * RCU if enabled and required. * * This needs to be done before the below as native_read_msr() * contains a tracepoint and x86_spec_ctrl_restore_host() calls * into world and some more. */ lockdep_hardirqs_off(CALLER_ADDR0); - guest_exit_irqoff(); + context_tracking_guest_exit(); instrumentation_begin(); trace_hardirqs_off_finish(); --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9236,6 +9236,15 @@ static int vcpu_enter_guest(struct kvm_v local_irq_disable(); kvm_after_interrupt(vcpu); + /* + * Wait until after servicing IRQs to account guest time so that any + * ticks that occurred while running the guest are properly accounted + * to the guest. Waiting until IRQs are enabled degrades the accuracy + * of accounting via context tracking, but the loss of accuracy is + * acceptable for all known use cases. + */ + vtime_account_guest_exit(); + if (lapic_in_kernel(vcpu)) { s64 delta = vcpu->arch.apic->lapic_timer.advance_expire_delta; if (delta != S64_MIN) {