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=-11.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 6070AC43460 for ; Tue, 20 Apr 2021 23:33:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 23434613E1 for ; Tue, 20 Apr 2021 23:33:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234398AbhDTXeQ (ORCPT ); Tue, 20 Apr 2021 19:34:16 -0400 Received: from mail.kernel.org ([198.145.29.99]:44882 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234280AbhDTXeO (ORCPT ); Tue, 20 Apr 2021 19:34:14 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 77BB661417; Tue, 20 Apr 2021 23:33:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1618961622; bh=8B7pNQVGVPqFq0OWNqhKIFYmTu1o9WldILSo9/Ljz44=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ktKbcgcxv4i8AftnZ+aGfR+j9fb32bPnaS8+Fh0aC/sUcA499GxKE/ACuBXcx+VRF Kuq+r6oCCf0lN3UOkHLSgQoUN4Y+qltj1eqKl2DDGzfdZ5bY3lYL2esbC+STr5MgpV wS6Z9RDUV6PgeP/00Yo+WNbmPCIl7lIGwpmO5ZC5PHG9eQPMV22a3hLYUoquYSGnrl coUtdC9rFeSVwLxrARypQm1oZ5dvEcGmSIYS3X9UQTU4R8PaPY5jt74AHKkUpI8fXM uBjjqVpW3i/Vl+bkcH+1Awb6nifw58rEuuLvr9jqc/krPgEsjkRPm7gEadtZ5Tb1IP vJ8wJGMrlxKbA== Date: Wed, 21 Apr 2021 01:33:38 +0200 From: Frederic Weisbecker To: Sean Christopherson Cc: Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Thomas Gleixner , Michael Tokarev , Christian Borntraeger Subject: Re: [PATCH v3 0/9] KVM: Fix tick-based accounting for x86 guests Message-ID: <20210420233338.GB8720@lothringen> References: <20210415222106.1643837-1-seanjc@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210415222106.1643837-1-seanjc@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 15, 2021 at 03:20:57PM -0700, Sean Christopherson wrote: > This is a continuation of Wanpeng's series[1] to fix tick-based CPU time > accounting on x86, with my cleanups[2] bolted on top. The core premise of > Wanpeng's patches are preserved, but they are heavily stripped down. > Specifically, only the "guest exit" paths are split, and no code is > consolidated. The intent is to do as little as possible in the three > patches that need to be backported. Keeping those changes as small as > possible also meant that my cleanups did not need to unwind much > refactoring. > > On x86, tested CONFIG_VIRT_CPU_ACCOUNTING_GEN =y and =n, and with > CONFIG_DEBUG_ENTRY=y && CONFIG_VALIDATE_STACKS=y. Compile tested arm64, > MIPS, PPC, and s390, the latter with CONFIG_DEBUG_ENTRY=y for giggles. > > One last note: I elected to use vtime_account_guest_exit() in the x86 code > instead of open coding these equivalents: > > if (vtime_accounting_enabled_this_cpu()) > vtime_guest_exit(current); > ... > if (!vtime_accounting_enabled_this_cpu()) > current->flags &= ~PF_VCPU; > > With CONFIG_VIRT_CPU_ACCOUNTING_GEN=n, this is a complete non-issue, but > for the =y case it means context_tracking_enabled_this_cpu() is being > checked back-to-back. The redundant checks bug me, but open coding the > gory details in x86 or providing funky variants in vtime.h felt worse. > > Delta from Wanpeng's v2: > > - s/context_guest/context_tracking_guest, purely to match the existing > functions. I have no strong opinion either way. > - Split only the "exit" functions. > - Partially open code vcpu_account_guest_exit() and > __vtime_account_guest_exit() in x86 to avoid churn when segueing into > my cleanups (see above). > > [1] https://lkml.kernel.org/r/1618298169-3831-1-git-send-email-wanpengli@tencent.com > [2] https://lkml.kernel.org/r/20210413182933.1046389-1-seanjc@google.com > > Sean Christopherson (6): > sched/vtime: Move vtime accounting external declarations above inlines > sched/vtime: Move guest enter/exit vtime accounting to vtime.h > context_tracking: Consolidate guest enter/exit wrappers > context_tracking: KVM: Move guest enter/exit wrappers to KVM's domain > KVM: x86: Consolidate guest enter/exit logic to common helpers > KVM: Move instrumentation-safe annotations for enter/exit to x86 code > > Wanpeng Li (3): > context_tracking: Move guest exit context tracking to separate helpers > context_tracking: Move guest exit vtime accounting to separate helpers > KVM: x86: Defer tick-based accounting 'til after IRQ handling > > arch/x86/kvm/svm/svm.c | 39 +-------- > arch/x86/kvm/vmx/vmx.c | 39 +-------- > arch/x86/kvm/x86.c | 8 ++ > arch/x86/kvm/x86.h | 52 ++++++++++++ > include/linux/context_tracking.h | 92 ++++----------------- > include/linux/kvm_host.h | 38 +++++++++ > include/linux/vtime.h | 138 +++++++++++++++++++------------ > 7 files changed, 204 insertions(+), 202 deletions(-) Please Cc me on any follow-up of this patchset. I have set up a lot of booby traps on purpose in this cave and I might be able to remember a few on the way. Should you meet one of the poisoned arrows, rest assured that you were not the aimed target though. Thanks.