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, USER_IN_DEF_DKIM_WL 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 F10CFC433ED for ; Wed, 28 Apr 2021 22:56:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C29F261440 for ; Wed, 28 Apr 2021 22:56:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229814AbhD1W5m (ORCPT ); Wed, 28 Apr 2021 18:57:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33360 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229624AbhD1W5l (ORCPT ); Wed, 28 Apr 2021 18:57:41 -0400 Received: from mail-pg1-x531.google.com (mail-pg1-x531.google.com [IPv6:2607:f8b0:4864:20::531]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 99A29C06138C for ; Wed, 28 Apr 2021 15:56:55 -0700 (PDT) Received: by mail-pg1-x531.google.com with SMTP id q10so45795373pgj.2 for ; Wed, 28 Apr 2021 15:56:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=j9J2Po6hg3Mws0Z8zIwA8YZmExUPMEbAlxsDVmpECto=; b=SGHxTwJlAK0ItXxEiNEHiyNq3bXcziNwt3q7yMHZXQWirJm5OGHF9HpvFMFKu4WSMp cKOyLBBhQrRV7g+JB2K3l6iUNdzCnw60IZDl+o1vVyRReZWT3cXzqR2YD/rpsDzOpiXS wBw6UVG52xR46FbG7sIwRJc1OOu1lnvuUQNK3GwLHF5V7fXkTaapTqy/Exvd05tF0Wkr wV5Z3r3tmE2YG9Zx4XIOq3FRm7x0fC+fWs/h0j5Or/z0X8psw2O9RAvGykngkvrG3dxs sRn7v8L1XI09Nl++tUaFZXtyfwt0ZOlAmgbz3f1snSOBBRx7fW5ieOkwbMVsfTSpTNSB bHdA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=j9J2Po6hg3Mws0Z8zIwA8YZmExUPMEbAlxsDVmpECto=; b=oM+BQxA1OjHGH8uI6zCl5L5Z2/brLCWazZfMLG1i/fWGyRi/5ZxSUJ1rP5CJ5b0pla 1rjNmORlyT8lnTAxl+0MeCwk21RE5MOw9iSwTi1uI3RSH8niCRi9MNUeXMgaMmovaLbr Dr06t07CQnGqQA0oHw4I1at2Zx0wSlhZQa31l/eAE/R8yV5teflsxxOzMqW44R2C0VSD MMC3LdSPWo1nBKcV78wtfPsIgIE6CCGrbv6P7zYlEiqzw7HTOAQxUg37bfHQdnN93U1R t++X0d1M078pMrIJ/DYORjz4RSHYRzLL7/lwaIAeTewCFOXuYz//WPj4dm6puhv7JDGf 5+Sw== X-Gm-Message-State: AOAM530H14u5MLCfaJe0ydwAnwaINqDtaMYc7gcIMWtRXHJ9dHKRCGE9 GeU3TfjTv9Rto4JNWyP6KlADQA== X-Google-Smtp-Source: ABdhPJx3OHZ8/hqLcVrY04nhXjnyxBow7PNlgjM6c+e7FkP3QPRVl0499+CVQL3qqh83h+bBiiUtOg== X-Received: by 2002:a62:170e:0:b029:1fa:7161:fd71 with SMTP id 14-20020a62170e0000b02901fa7161fd71mr29938355pfx.35.1619650614924; Wed, 28 Apr 2021 15:56:54 -0700 (PDT) Received: from google.com (240.111.247.35.bc.googleusercontent.com. [35.247.111.240]) by smtp.gmail.com with ESMTPSA id e5sm142067pgj.91.2021.04.28.15.56.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Apr 2021 15:56:54 -0700 (PDT) Date: Wed, 28 Apr 2021 22:56:50 +0000 From: Sean Christopherson To: Wanpeng Li Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel Subject: Re: [PATCH] KVM: LAPIC: Accurately guarantee busy wait for timer to expire when using hv_timer Message-ID: References: <1619608082-4187-1-git-send-email-wanpengli@tencent.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1619608082-4187-1-git-send-email-wanpengli@tencent.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, Apr 28, 2021, Wanpeng Li wrote: > From: Wanpeng Li > > Commit ee66e453db13d (KVM: lapic: Busy wait for timer to expire when > using hv_timer) tries to set ktime->expired_tscdeadline by checking > ktime->hv_timer_in_use since lapic timer oneshot/periodic modes which > are emulated by vmx preemption timer also get advanced, they leverage > the same vmx preemption timer logic with tsc-deadline mode. However, > ktime->hv_timer_in_use is cleared before apic_timer_expired() handling, > let's delay this clearing in preemption-disabled region. > > Fixes: ee66e453db13d (KVM: lapic: Busy wait for timer to expire when using hv_timer) Well that's embarassing. I suspect/hope I tested the case where start_hv_timer() detects the timer already expired. On the plus side, start_hv_timer() calls cancel_hv_timer() after apic_timer_expired(), so there are unlikely to be hidden side effects (and cancel_hv_timer() is tiny). > Cc: Sean Christopherson > Signed-off-by: Wanpeng Li Reviewed-by: Sean Christopherson > --- > arch/x86/kvm/lapic.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > index 152591f..c0ebef5 100644 > --- a/arch/x86/kvm/lapic.c > +++ b/arch/x86/kvm/lapic.c > @@ -1913,8 +1913,8 @@ void kvm_lapic_expired_hv_timer(struct kvm_vcpu *vcpu) > if (!apic->lapic_timer.hv_timer_in_use) > goto out; > WARN_ON(rcuwait_active(&vcpu->wait)); > - cancel_hv_timer(apic); > apic_timer_expired(apic, false); > + cancel_hv_timer(apic); > > if (apic_lvtt_period(apic) && apic->lapic_timer.period) { > advance_periodic_target_expiration(apic); > -- > 2.7.4 >