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=-23.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, 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_IN_DEF_DKIM_WL autolearn=ham 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 06DE0C433ED for ; Mon, 17 May 2021 16:50:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D7EC261028 for ; Mon, 17 May 2021 16:50:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236764AbhEQQvP (ORCPT ); Mon, 17 May 2021 12:51:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43214 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240906AbhEQQvE (ORCPT ); Mon, 17 May 2021 12:51:04 -0400 Received: from mail-il1-x12c.google.com (mail-il1-x12c.google.com [IPv6:2607:f8b0:4864:20::12c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 35499C075389 for ; Mon, 17 May 2021 09:35:04 -0700 (PDT) Received: by mail-il1-x12c.google.com with SMTP id z1so6680852ils.0 for ; Mon, 17 May 2021 09:35:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=8XjCzUGwVIiP3+YZrLjLAcXTaHRHGnoKVgLiqwR9S0M=; b=Q6bRC7J4OtYLgKndA++vo/4BHK+kvEiFv6aZ8jWWH77vI3wtldPu8UuBa/t1erlYQM T9idF8OhWYtD4zivdzckr+jwdarqAhWdL9CsBic6mokrIQJq4owNlFkKFmTYWAlWgF1S buzzozZu0YuX24RDIBlPoWalnO7Y8mpaLV+LZ4JC7Z7vgp4pk/rjuft2exRvDVyZo05N UnayAVciQIo5al9hYnYbt+HnJkklbO7h56O5J6IZfcUnUGM0hJMghwzRvT0ezkG8wAUU 1Q8Is/HVfDrTV5SZUAMLudhbv00hpSn56L6Tm7auH3RSOIUMUJLNHSv9g6ASVHr+kh0D 88HQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=8XjCzUGwVIiP3+YZrLjLAcXTaHRHGnoKVgLiqwR9S0M=; b=iDdndN18Q/6PpxOg35YZuNf8Vf3CioAX7KNCEDpuA3BN+eMwLL1VsrhBUX0l/0h2iK fHfv8I0yIUsIqbRmLXybldDznID6jwLfvorgmcctz/MBtOxV/2n/YX4BzFcChs/FwwwV 0tFZ5gak1ewLi/tJ/kGnaz4KwU5SRBuT2b8UKz2tOMLUuI+pfJtQtg3OLzpeSvz+79hv Wb6yzC/h/DzOiVRatOq4SlVnNHRrPu3hgJ8reze8zD8zgODEzYHmSyYzbKL+7ILsvAoJ NMkwWgrEfFetBtAM02KKqWdxeHMWW7sG1/AnqOaSkBEE8hrZVr9wNP9tjecqraecjKbN +yQw== X-Gm-Message-State: AOAM531ntT2j6ZHebMuKIm6PTbN0rxpXI6NHogE/Z7bSPqbG5Jf2MFUI E+uuYpVqKaVhZC5VYOM72Xj4rpdovTJ1VVTdKk+DGQ== X-Google-Smtp-Source: ABdhPJz0NB7vJP6/zgoqy7G+HsgYZlposuUO5ZTrETUd2kYON8RUI88LoaUUJPMRD7ZtJUnnXCq7UIfwvLcbolZTWsY= X-Received: by 2002:a92:cda5:: with SMTP id g5mr457366ild.245.1621269303543; Mon, 17 May 2021 09:35:03 -0700 (PDT) MIME-Version: 1.0 References: <1621260028-6467-1-git-send-email-wanpengli@tencent.com> In-Reply-To: <1621260028-6467-1-git-send-email-wanpengli@tencent.com> From: David Matlack Date: Mon, 17 May 2021 09:34:38 -0700 Message-ID: Subject: Re: [PATCH v3 1/5] KVM: exit halt polling on need_resched() for both book3s and generic halt-polling To: Wanpeng Li Cc: linux-kernel@vger.kernel.org, kvm list , Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Ben Segall , Venkatesh Srinivas , Paul Mackerras , Suraj Jitindar Singh Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, May 17, 2021 at 7:01 AM Wanpeng Li wrote: > > From: Wanpeng Li > > Inspired by commit 262de4102c7bb8 (kvm: exit halt polling on need_resched() > as well), CFS_BANDWIDTH throttling will use resched_task() when there is just > one task to get the task to block. It was likely allowing VMs to overrun their > quota when halt polling. Due to PPC implements an arch specific halt polling > logic, we should add the need_resched() checking there as well. This > patch adds a helper function that to be shared between book3s and generic > halt-polling loop. > > Cc: Ben Segall > Cc: Venkatesh Srinivas > Cc: Jim Mattson > Cc: David Matlack > Cc: Paul Mackerras > Cc: Suraj Jitindar Singh > Signed-off-by: Wanpeng Li Reviewed-by: David Matlack > --- > v2 -> v3: > * add a helper function > v1 -> v2: > * update patch description > > arch/powerpc/kvm/book3s_hv.c | 2 +- > include/linux/kvm_host.h | 2 ++ > virt/kvm/kvm_main.c | 9 +++++++-- > 3 files changed, 10 insertions(+), 3 deletions(-) > > diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c > index 28a80d240b76..360165df345b 100644 > --- a/arch/powerpc/kvm/book3s_hv.c > +++ b/arch/powerpc/kvm/book3s_hv.c > @@ -3936,7 +3936,7 @@ static void kvmppc_vcore_blocked(struct kvmppc_vcore *vc) > break; > } > cur = ktime_get(); > - } while (single_task_running() && ktime_before(cur, stop)); > + } while (kvm_vcpu_can_block(cur, stop)); > > spin_lock(&vc->lock); > vc->vcore_state = VCORE_INACTIVE; > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 2f34487e21f2..bf4fd60c4699 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -1583,4 +1583,6 @@ static inline void kvm_handle_signal_exit(struct kvm_vcpu *vcpu) > /* Max number of entries allowed for each kvm dirty ring */ > #define KVM_DIRTY_RING_MAX_ENTRIES 65536 > > +bool kvm_vcpu_can_block(ktime_t cur, ktime_t stop); > + > #endif > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 6b4feb92dc79..c81080667fd1 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -2945,6 +2945,12 @@ update_halt_poll_stats(struct kvm_vcpu *vcpu, u64 poll_ns, bool waited) > vcpu->stat.halt_poll_success_ns += poll_ns; > } > > + > +bool kvm_vcpu_can_block(ktime_t cur, ktime_t stop) nit: kvm_vcpu_can_poll() would be a more accurate name for this function. > +{ > + return single_task_running() && !need_resched() && ktime_before(cur, stop); > +} > + > /* > * The vCPU has executed a HLT instruction with in-kernel mode enabled. > */ > @@ -2973,8 +2979,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu) > goto out; > } > poll_end = cur = ktime_get(); > - } while (single_task_running() && !need_resched() && > - ktime_before(cur, stop)); > + } while (kvm_vcpu_can_block(cur, stop)); > } > > prepare_to_rcuwait(&vcpu->wait); > -- > 2.25.1 >