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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 70D8AC433B4 for ; Mon, 26 Apr 2021 15:09:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2B51461176 for ; Mon, 26 Apr 2021 15:09:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233988AbhDZPKb (ORCPT ); Mon, 26 Apr 2021 11:10:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55774 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233573AbhDZPKa (ORCPT ); Mon, 26 Apr 2021 11:10:30 -0400 Received: from mail-pf1-x433.google.com (mail-pf1-x433.google.com [IPv6:2607:f8b0:4864:20::433]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 48BEFC061574 for ; Mon, 26 Apr 2021 08:09:49 -0700 (PDT) Received: by mail-pf1-x433.google.com with SMTP id y62so6510478pfg.4 for ; Mon, 26 Apr 2021 08:09:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amacapital-net.20150623.gappssmtp.com; s=20150623; h=content-transfer-encoding:from:mime-version:subject:date:message-id :references:cc:in-reply-to:to; bh=jkRMHjrSCZPTvq0vYCKIhPuB3sHp9mEl5+KCAGLgqhY=; b=BC255GuEXgIFcphCVXnJjpn/yY9uAy6wVw0MRO1UsJsMZHgxebRSh2+QI57//qMEyv Zu9Fcb43MIJ3HFmP9knQRNBGE1bZkWDlhGHRd2IWxjzrA/NvYcyh+vl9m5l32uOo2Yjh Cdek7gxGFBhwIHLiMA7bTKHzzNu2Ou+7KeDXI9fgqxYw24a1DEDTqkqfvp7hE6GOFdFr tS6CkxhefAh4haOT88fqCaYG5uGq7ae45bkMSnwWV88YB3N4Naz2F1TiV2z/iXAxvouM Wd+QwvRxOSY2hC4KURCitUE9yheLl76gidD/qy43skuLSF+NHoOi84Y/eF+MaiEIkPsg lKsg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:content-transfer-encoding:from:mime-version :subject:date:message-id:references:cc:in-reply-to:to; bh=jkRMHjrSCZPTvq0vYCKIhPuB3sHp9mEl5+KCAGLgqhY=; b=GGorbdvp5JiByD4s8g/Nh4qzWSsxR3elwJ8szforZEl+T4hN1s7KdcauqRKugJfr2V bBTjFNNKIMKnl0x86OKSWhTVGsqzvg3L0P97sRYQFtRs3s3ZMma6TjZxekgpG+L3ZVTn pO50xPndjoNlO98UlxCjQskaTZImJADmm08L11ZCb9VKCdxzwJLpd6cvPnf+3nkT7U4y 8D7Uzb7pFGgpQSwlM8pO+ShCADlZ6TMrel0Z2eFVDc2rKT+u2SjX+ceEgCRbg3qFN8jN FyDfqGTuZgUP3iQ7eIMLdqzYS5eONGxhiR3gC7Jw/1Znq5DmbJtuwsOldHXhSJMRcN3g zwsA== X-Gm-Message-State: AOAM532FVVACHCQw7iscjRzxlvs06Wgn1liGhiwz1/TB5eco/Iq1zi/F ObuO9TXgtn/VdQIhLlhemy8LCw== X-Google-Smtp-Source: ABdhPJycw88+zgGR+lUaMUyVXFbk30NVIRdTViB8sEDFCafSyfaBak/frZMBGh2Hror9H6AOCJeNLQ== X-Received: by 2002:a63:1f25:: with SMTP id f37mr6637053pgf.142.1619449788778; Mon, 26 Apr 2021 08:09:48 -0700 (PDT) Received: from ?IPv6:2603:8001:6301:5a88:95bc:39d4:dfd7:ed9e? (2603-8001-6301-5a88-95bc-39d4-dfd7-ed9e.res6.spectrum.com. [2603:8001:6301:5a88:95bc:39d4:dfd7:ed9e]) by smtp.gmail.com with ESMTPSA id o15sm15512939pjk.48.2021.04.26.08.09.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 26 Apr 2021 08:09:48 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable From: Andy Lutomirski Mime-Version: 1.0 (1.0) Subject: Re: [PATCH v2 2/2] KVM: VMX: Invoke NMI handler via indirect call instead of INTn Date: Mon, 26 Apr 2021 08:09:46 -0700 Message-Id: References: <20210426145104.GW1401198@tassilo.jf.intel.com> Cc: Paolo Bonzini , Lai Jiangshan , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, LKML , Josh Poimboeuf , Uros Bizjak , Andy Lutomirski , Steven Rostedt In-Reply-To: <20210426145104.GW1401198@tassilo.jf.intel.com> To: Andi Kleen X-Mailer: iPhone Mail (18D70) Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org > On Apr 26, 2021, at 7:51 AM, Andi Kleen wrote: >=20 > =EF=BB=BF >>=20 >>> The original code "int $2" can provide the needed CPU-hidden-NMI-masked >>> when entering #NMI, but I doubt it about this change. >>=20 >> How would "int $2" block NMIs? The hidden effect of this change (and I >> should have reviewed better the effect on the NMI entry code) is that the= >> call will not use the IST anymore. >=20 > My understanding is that int $2 does not block NMIs. >=20 > So reentries might have been possible. >=20 The C NMI code has its own reentrancy protection and has for years. It shou= ld work fine for this use case. > -Andi