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=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 5BA20C433ED for ; Thu, 8 Apr 2021 16:56:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2E933610A2 for ; Thu, 8 Apr 2021 16:56:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231732AbhDHQ4i (ORCPT ); Thu, 8 Apr 2021 12:56:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56488 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231699AbhDHQ4i (ORCPT ); Thu, 8 Apr 2021 12:56:38 -0400 Received: from mail-pg1-x52b.google.com (mail-pg1-x52b.google.com [IPv6:2607:f8b0:4864:20::52b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0D591C061760 for ; Thu, 8 Apr 2021 09:56:27 -0700 (PDT) Received: by mail-pg1-x52b.google.com with SMTP id p12so1815552pgj.10 for ; Thu, 08 Apr 2021 09:56:27 -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=FfNWWgdKdl9R3c8saiXMYMVU97LjgEbiqFdKW/3lJXg=; b=WFgtnS5NoKTB+ZP6o9d1NkasuXh5ajH+f/ry0L2iI6fB0e4/RJW2i7aGpMeuWAopOC mFbJtebwpT08W/9H8wvIETf6JcWKo0Vvtb5KcmEu8TZlJ6QMa6jECD4llYw7abiVXIPS hSRdpmBRbiMqs5LJbh0G3sHC7iME0eo1VBloo5VlQtt4B6Tq50nBLzuKtQB9491memvn J5VH3lrqLENAUn6A4L92AZjH1m0HoMsIHI57i289OUkjN1Xatz5eSu80brcJI1tMkptZ qqU0UEPTHY1nZUYgv70Km8tmR0Mw2puChjwx9L0s+RBwujrGSVZXQMTg+bC+3Fe49zdT zgdw== 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=FfNWWgdKdl9R3c8saiXMYMVU97LjgEbiqFdKW/3lJXg=; b=UkJf/5uIdoB0SZwMK7el8WuEUxL2jDuDw2fZ/r4X9cZWk4+16L9tTm/OOGfkFR7Nx+ GRUT9i3fhxkQ51yPriVVADD+R6RkAzTgSafCL8EkCMJ6mFaCqDhl/F9+R3SPg8zX5v5s jGaF7PQ9gHBpAmvxD8VkFxv4SvS2Dqq+tzMZQMViucPjYlYqbA7QY1Rs68O6ZSPi+1W+ wLk9iO8YFyOhg+3Hz4qnkbZk4Q8KEKM1uL57BjjkAC1uyI0OK8sbrs+VhAWLXVKCCaaa zS33NVWkyEJl8a7YGzkS8p/5Jb8BGo8S5j2nepVbtjoLDERrhhCy6RC1EejT3xBaMPNR 2YPA== X-Gm-Message-State: AOAM533O1QS1q3/IdPSIIFu3HV1Og5arEhcI2fmGDix46EayTusSeCHB /tD6TTVOoUmDK2JzHOlTuiWE0A== X-Google-Smtp-Source: ABdhPJx0bYX1CLTWtqLHar66ui00ZkBdtoTTFFJnWejqc8Sunz6Gt5WRmNTXUPkVa/xZyEI4YS/9ig== X-Received: by 2002:a65:4985:: with SMTP id r5mr8845677pgs.65.1617900986405; Thu, 08 Apr 2021 09:56:26 -0700 (PDT) Received: from google.com (240.111.247.35.bc.googleusercontent.com. [35.247.111.240]) by smtp.gmail.com with ESMTPSA id u18sm54005pfm.4.2021.04.08.09.56.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Apr 2021 09:56:25 -0700 (PDT) Date: Thu, 8 Apr 2021 16:56:22 +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: X86: Do not yield to self Message-ID: References: <1617880989-8019-1-git-send-email-wanpengli@tencent.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1617880989-8019-1-git-send-email-wanpengli@tencent.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Apr 08, 2021, Wanpeng Li wrote: > From: Wanpeng Li > > If the target is self we do not need to yield, we can avoid malicious > guest to play this. > > Signed-off-by: Wanpeng Li > --- > Rebased on https://lore.kernel.org/kvm/1617697935-4158-1-git-send-email-wanpengli@tencent.com/ > > arch/x86/kvm/x86.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 43c9f9b..260650f 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -8230,6 +8230,10 @@ static void kvm_sched_yield(struct kvm_vcpu *vcpu, unsigned long dest_id) > if (!target) > goto no_yield; > > + /* yield to self */ If you're going to bother with a comment, maybe elaborate a bit, e.g. /* Ignore requests to yield to self. */ > + if (vcpu->vcpu_id == target->vcpu_id) > + goto no_yield; > + > if (!READ_ONCE(target->ready)) > goto no_yield; > > -- > 2.7.4 >