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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 43DA4C433F5 for ; Tue, 5 Oct 2021 17:59:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2453560F38 for ; Tue, 5 Oct 2021 17:59:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234590AbhJESBL (ORCPT ); Tue, 5 Oct 2021 14:01:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38880 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232861AbhJESBL (ORCPT ); Tue, 5 Oct 2021 14:01:11 -0400 Received: from mail-pf1-x42e.google.com (mail-pf1-x42e.google.com [IPv6:2607:f8b0:4864:20::42e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A9464C061749 for ; Tue, 5 Oct 2021 10:59:20 -0700 (PDT) Received: by mail-pf1-x42e.google.com with SMTP id c29so224428pfp.2 for ; Tue, 05 Oct 2021 10:59:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=FxQLMgGRO5NBtnXquaGOaBTErWmCv8I3xPuDWnsxNMk=; b=F/KUJ9KxvEsNAjAVArIa0Y5aSmAOz+aJizqcj2pzEi4qJIqB2IFX721Kul6kz5kLAk PjBMso41i9Y9+C/F9DiS0p0+oXBsCty3RDqZgqbbk7JhDkLpNWOLMaod+AkU5w9M+bQh cSfoLqKsr8fsu/q1vGLM4OQ5i2bsABFIVw50jOA9V4SdE69T//VGievgTDNSkz6g2FW5 ywFBo7aaXTXuQ0enIhO0C0qldeh8b+ZZe9mX7VhIYvJ3wPlBe+8MO3iGtw7PPNpB941P D8jfduAnnYVRFUx6RNBNINJHbqpFo28BSGzUxp9S1zGzPVklF+6nc0d5dIpaHnKuaJ4a fduQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=FxQLMgGRO5NBtnXquaGOaBTErWmCv8I3xPuDWnsxNMk=; b=EiZr3u1ahqaAwv8WVlwG1ErZyinl0MV2n+c4jG1SsIVb/yeVGo8sCBj4hYoB9927hl J54trSQmTEaHwE39ukBPShSbJ+i5upXlog8Fy55KxgzF88t2xdhR/Slan/dswKQtrXE7 TiVlyCmFAJj8y4czAg3/S2ScTekDRA7vI4kut7vD6aGmlXOI4RmIe535OT5h9e69Wjwi j4nIUP5Thhn5vzqCQEyfU2aURZ0qT0kitYbYzmvArTzBdRsHeNf+lsLNTocKm/iMih2U Cc5cKZi5mPbaeiB7xM4dgmZPrmtyZNgS0vGClo6Z/eLYQpL80XECxJW/MHxkhpcUYtL1 9PGQ== X-Gm-Message-State: AOAM532HRI3oXK7FkYXmxrNWAbU7YD3mf0iQuIjUXR0DGe3fAWvFwr/p bFQ9mYJnIVca0J4/3BtrjEVm+Q== X-Google-Smtp-Source: ABdhPJzvVlqiWZpWASSuAm/r4Q17GWyjK/l1ppJ7hO/LiK5cR5a8MOruJ6kp1JRzp7Z0vC/UvOK+HQ== X-Received: by 2002:aa7:96e3:0:b0:44c:83be:19bc with SMTP id i3-20020aa796e3000000b0044c83be19bcmr4103166pfq.37.1633456759988; Tue, 05 Oct 2021 10:59:19 -0700 (PDT) Received: from google.com (157.214.185.35.bc.googleusercontent.com. [35.185.214.157]) by smtp.gmail.com with ESMTPSA id d9sm17876808pgn.64.2021.10.05.10.59.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 Oct 2021 10:59:19 -0700 (PDT) Date: Tue, 5 Oct 2021 17:59:16 +0000 From: Sean Christopherson To: Jim Mattson Cc: Robert Hoo , pbonzini@redhat.com, vkuznets@redhat.com, wanpengli@tencent.com, joro@8bytes.org, kvm@vger.kernel.org, yu.c.zhang@linux.intel.com Subject: Re: [PATCH v1 3/5] KVM: x86: nVMX: VMCS12 field's read/write respects field existence bitmap Message-ID: References: <3ac79d874fb32c6472151cf879edfb2f1b646abf.camel@linux.intel.com> <0b94844844521fc0446e3df0aa02d4df183f8107.camel@linux.intel.com> <64aad01b6bffd70fa3170cf262fe5d7c66f6b2d4.camel@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, Oct 05, 2021, Jim Mattson wrote: > On Tue, Oct 5, 2021 at 9:16 AM Sean Christopherson wrote: > > > > On Tue, Sep 28, 2021, Robert Hoo wrote: > > > On Fri, 2021-09-03 at 15:11 +0000, Sean Christopherson wrote: > > > You also said, "This is quite the complicated mess for > > > something I'm guessing no one actually cares about. At what point do > > > we chalk this up as a virtualization hole and sweep it under the rug?" > > > -- I couldn't agree more. > > > > ... > > > > > So, Sean, can you help converge our discussion and settle next step? > > > > Any objection to simply keeping KVM's current behavior, i.e. sweeping this under > > the proverbial rug? > > Adding 8 KiB per vCPU seems like no big deal to me, but, on the other > hand, Paolo recently argued that slightly less than 1 KiB per vCPU was > unreasonable for VM-exit statistics, so maybe I've got a warped > perspective. I'm all for pedantic adherence to the specification, but > I have to admit that no actual hypervisor is likely to care (or ever > will). It's not just the memory, it's also the complexity, e.g. to get VMCS shadowing working correctly, both now and in the future.