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[23.128.96.18]) by mx.google.com with ESMTP id y8si11517445edc.456.2021.05.11.03.30.35; Tue, 11 May 2021 03:30:59 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=NHjn3pGy; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231317AbhEKKaJ (ORCPT + 99 others); Tue, 11 May 2021 06:30:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50704 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229935AbhEKKaI (ORCPT ); Tue, 11 May 2021 06:30:08 -0400 Received: from mail-ot1-x331.google.com (mail-ot1-x331.google.com [IPv6:2607:f8b0:4864:20::331]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 83F82C061574; Tue, 11 May 2021 03:29:02 -0700 (PDT) Received: by mail-ot1-x331.google.com with SMTP id q7-20020a9d57870000b02902a5c2bd8c17so17081940oth.5; Tue, 11 May 2021 03:29:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=zQB0PqP12TFHAd0NTVcth9DgppuMURJYYCn1jtkYIJ8=; b=NHjn3pGyGWaimt9x9gYKbRfEtgKJWgkBh17mD8PILXdnCpWzdRkqoZDl+ncj/G8tzr HA4NbjE9UJuDWBFL+gf5KrCP/3ZlWJjZD5+ElfgS1l6ElA5p5AWl7hsSXDibAXUXaJCB cV4LHTvY/gAlIZXkYtNoIi/PxCx70vnfKgEgGgEblmz0lmpWZHh/Xal0Vy3kYivOeHzh cXXzrz0cd8YxnXEbcklLpiiygCHz1+fnNJg9aOuT2D8iTWWDDriYmSdsWMCx6TcyuBze 0+eiXgcw+QQGA3TrcWKvYGV/mDIierY8A8diPYoSf2Tgknssn5v/Y47GCyw5UXsaKwDJ 9YqA== 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=zQB0PqP12TFHAd0NTVcth9DgppuMURJYYCn1jtkYIJ8=; b=Z6sVBeLA2DMC8w3iDuG10vr8DCdo1EV1cvg8A2r2RX8oSAgC2tpjErYmXlCfZiiuXr vhBmLGX185R8HBjD+6AKQEcRwcLCdMkH0TAHI1ZXeSAN86ngJmG6H56lmXE226BxeBcD FwmuZU+nrEVE6Phf1JmV1FdEXYhBSkS/FGzX8rUDB9G+AO1r3NGgMoLQkoQLLdEpK9sv 4TqoXQxtcBcfZqkEAUUYIOhr2stILYpg+Bta5W6V057ber613PQysUNXxil3QMHkGJ0s U0qkrnGfNTiIdarh+yRnKnVoOHxezpf7VkPcd7N85VAP9Ap1oCKLqagFYsN1ORLTPMId ydPQ== X-Gm-Message-State: AOAM532kpDPxbDiA7dJjTa+y743RK+Td49VETe/Y+JjnijdLYNMVDaLe vsDCdiX4eBXUdSqBEiUrSofx3Mf2LHUTe0B1xgU= X-Received: by 2002:a9d:7a88:: with SMTP id l8mr17468192otn.185.1620728942017; Tue, 11 May 2021 03:29:02 -0700 (PDT) MIME-Version: 1.0 References: <1620466310-8428-1-git-send-email-wanpengli@tencent.com> <1620466310-8428-3-git-send-email-wanpengli@tencent.com> In-Reply-To: From: Wanpeng Li Date: Tue, 11 May 2021 18:28:51 +0800 Message-ID: Subject: Re: [PATCH 3/3] KVM: X86: Fix vCPU preempted state from guest point of view To: Sean Christopherson Cc: LKML , kvm , Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , "# v3 . 10+" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 11 May 2021 at 08:18, Sean Christopherson wrote: > > On Sat, May 08, 2021, Wanpeng Li wrote: > > From: Wanpeng Li > > > > Commit 66570e966dd9 (kvm: x86: only provide PV features if enabled in guest's > > CPUID) avoids to access pv tlb shootdown host side logic when this pv feature > > is not exposed to guest, however, kvm_steal_time.preempted not only leveraged > > by pv tlb shootdown logic but also mitigate the lock holder preemption issue. > > From guest point of view, vCPU is always preempted since we lose the reset of > > kvm_steal_time.preempted before vmentry if pv tlb shootdown feature is not > > exposed. This patch fixes it by clearing kvm_steal_time.preempted before > > vmentry. > > > > Fixes: 66570e966dd9 (kvm: x86: only provide PV features if enabled in guest's CPUID) > > Cc: stable@vger.kernel.org > > Signed-off-by: Wanpeng Li > > --- > > arch/x86/kvm/x86.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > > index c0244a6..c38e990 100644 > > --- a/arch/x86/kvm/x86.c > > +++ b/arch/x86/kvm/x86.c > > @@ -3105,7 +3105,8 @@ static void record_steal_time(struct kvm_vcpu *vcpu) > > st->preempted & KVM_VCPU_FLUSH_TLB); > > if (xchg(&st->preempted, 0) & KVM_VCPU_FLUSH_TLB) > > kvm_vcpu_flush_tlb_guest(vcpu); > > - } > > + } else > > + st->preempted = 0; > > Curly braces needed since the if-statment needs 'em. Other than that, Will send out a new version after 1-2 get reviewed. :) > > Reviewed-by: Sean Christopherson > > > > > vcpu->arch.st.preempted = 0; > > > > -- > > 2.7.4 > >