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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EF016C433EF for ; Wed, 9 Mar 2022 17:00:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236706AbiCIRBr (ORCPT ); Wed, 9 Mar 2022 12:01:47 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41868 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235812AbiCIRBB (ORCPT ); Wed, 9 Mar 2022 12:01:01 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id DC4FB1052AF for ; Wed, 9 Mar 2022 08:47:58 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1646844461; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=GtHZAmMaUYAx0LRBNry1Z8g5yS/lTA9TMVV6Zdqr9HI=; b=BYfrRTalkZ7ByBaYceTjXgQMZ8rw5k4wRj7NlM4FQOrjeGqY9eTRUhlBjPvn+A89TpShO2 OtOC3QX8nXF6dzvFPF7aNxzGr3+fXj3/XSmFumX02tdMHzgJPQGe1EDmGuMDYOP6Nuc+zT q97VgYpSiuPSEqYgdO5pz3pjA9Mfmi0= Received: from mail-ej1-f69.google.com (mail-ej1-f69.google.com [209.85.218.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-274--FDnHRUINxOZlu-W9BcJUQ-1; Wed, 09 Mar 2022 11:47:39 -0500 X-MC-Unique: -FDnHRUINxOZlu-W9BcJUQ-1 Received: by mail-ej1-f69.google.com with SMTP id 13-20020a170906328d00b006982d0888a4so1594057ejw.9 for ; Wed, 09 Mar 2022 08:47:38 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=GtHZAmMaUYAx0LRBNry1Z8g5yS/lTA9TMVV6Zdqr9HI=; b=SakN3tsyfF85tuaBhLLOFrn3E+bFbi8J1Yy6+wC5+K0eC5Q05cVRiVGAa0BoIJr7Zu 53M8SIeCbNhYhyiitDqPn54xJOJ7y1rG88CPRsl2rWQ1V91p42tjHY38Twq7p6akQUWW 88Ruzcmr3DFEH6xzRm4bZDygtxmuEAPLOlccZkcPETcST82VzYYp+Bji97ohDrxO0Vas //6yPNdjSPT03BAesBG6hG6jkCni9iNPpzFNQMM25DPXdSMTTD9qCK/AHYxCYSTYQw96 o5EymtjYqEgzMC+ExAd/quqrgV/Ekb953q2F5P9RMcADfJ1mPxily4jXLxTJvmeZ1KI2 d26w== X-Gm-Message-State: AOAM533CAPcuFFgKMwSBV3iKwSGeWij9a6jk9jm/6UiLMv0kw5/jg3ut oIbTCIxTVWrRhHwlFWc2h1RvgG6w992Ooi+H9GWvnK50Y+7NvAHc/C2xmk+3ZMG1a6HaErnqz75 y4ddoP0g3BxrjOaHIWSwyJgAT X-Received: by 2002:a17:907:60ca:b0:6da:8f25:7983 with SMTP id hv10-20020a17090760ca00b006da8f257983mr631820ejc.106.1646844457789; Wed, 09 Mar 2022 08:47:37 -0800 (PST) X-Google-Smtp-Source: ABdhPJw7W66bmqFbu8gYAU5N0gz7/+fCQJtGeEoAcf1WlMCvUxsd/Rx1EWoj8m+ZeeL+r81lz05NDA== X-Received: by 2002:a17:907:60ca:b0:6da:8f25:7983 with SMTP id hv10-20020a17090760ca00b006da8f257983mr631795ejc.106.1646844457559; Wed, 09 Mar 2022 08:47:37 -0800 (PST) Received: from ?IPV6:2001:b07:6468:f312:c8dd:75d4:99ab:290a? ([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.googlemail.com with ESMTPSA id t14-20020a170906608e00b006d1455acc62sm908648ejj.74.2022.03.09.08.47.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 09 Mar 2022 08:47:36 -0800 (PST) Message-ID: <63493d06-0b6c-9993-2315-64033dd041d6@redhat.com> Date: Wed, 9 Mar 2022 17:47:35 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH MANUALSEL 5.15] KVM: x86: Yield to IPI target vCPU only if it is busy Content-Language: en-US To: Sasha Levin , linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Li RongQing , tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, kvm@vger.kernel.org References: <20220309164632.137995-1-sashal@kernel.org> From: Paolo Bonzini In-Reply-To: <20220309164632.137995-1-sashal@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/9/22 17:46, Sasha Levin wrote: > From: Li RongQing > > [ Upstream commit 9ee83635d872812f3920209c606c6ea9e412ffcc ] > > When sending a call-function IPI-many to vCPUs, yield to the > IPI target vCPU which is marked as preempted. > > but when emulating HLT, an idling vCPU will be voluntarily > scheduled out and mark as preempted from the guest kernel > perspective. yielding to idle vCPU is pointless and increase > unnecessary vmexit, maybe miss the true preempted vCPU > > so yield to IPI target vCPU only if vCPU is busy and preempted > > Signed-off-by: Li RongQing > Message-Id: <1644380201-29423-1-git-send-email-lirongqing@baidu.com> > Signed-off-by: Paolo Bonzini > Signed-off-by: Sasha Levin > --- > arch/x86/kernel/kvm.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c > index b656456c3a94..49f19e572a25 100644 > --- a/arch/x86/kernel/kvm.c > +++ b/arch/x86/kernel/kvm.c > @@ -565,7 +565,7 @@ static void kvm_smp_send_call_func_ipi(const struct cpumask *mask) > > /* Make sure other vCPUs get a chance to run if they need to. */ > for_each_cpu(cpu, mask) { > - if (vcpu_is_preempted(cpu)) { > + if (!idle_cpu(cpu) && vcpu_is_preempted(cpu)) { > kvm_hypercall1(KVM_HC_SCHED_YIELD, per_cpu(x86_cpu_to_apicid, cpu)); > break; > } NACK