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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 63385C433E0 for ; Thu, 28 May 2020 11:14:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 35D75208A7 for ; Thu, 28 May 2020 11:14:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Y7xw0WXi" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388201AbgE1LOH (ORCPT ); Thu, 28 May 2020 07:14:07 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:43396 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2388080AbgE1LOG (ORCPT ); Thu, 28 May 2020 07:14:06 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1590664444; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=acpHxn1a0do1eYSDNn0Gj48JIN5rgon7KXnl2Z/Teo8=; b=Y7xw0WXiHEHQIhT2bjq91wOHPfPQwA89ylTlhlq12nEm9tvZlaTKwmYhpZwg4CS95tHe0f USU2VAi4SnM1XQ9bghdi0kvohbiw5DDN4KUn+KKdScQw1psF8qYPb4XuJBGjRccz9wn/F8 W15k92yiy6Ic+FKXfyT+x3YX/7yWask= Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-201-T3WXmPhmPpq1_29llSJ7-A-1; Thu, 28 May 2020 07:14:03 -0400 X-MC-Unique: T3WXmPhmPpq1_29llSJ7-A-1 Received: by mail-ed1-f72.google.com with SMTP id bo26so11334712edb.22 for ; Thu, 28 May 2020 04:14:03 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:in-reply-to:references:date :message-id:mime-version; bh=acpHxn1a0do1eYSDNn0Gj48JIN5rgon7KXnl2Z/Teo8=; b=eozQ5MPmlXZIvzR+VKRmvbMGUgtG6UijTFtlB2bTKjgbYYsCxSdev6NvlgE/kzGp53 r9qHOZbR3yzE935IgqkN/EHLWBnjutddnhBEB3FeaUQjDOZuRVD6eghIea54zI5ynGEs 9/dFRAhih9davg9z49V2ji4aDktcsUX7OSTkP9Yngl0EUYMNozFiCX2BNkOPTiTHCwTn zPLQnxgxWk3txEJ3KZCDS6UhR1ZNgcJNquuKmdLmdfv0EVIAE9pAVn3fear+ddXkUIc2 RhGPnZq3Jl0k66j7IKSIAYYtY0eVSSNX4np5E23cmHuL/GrW5VI/BKSXyKRC9MRbK5Pe 7y3g== X-Gm-Message-State: AOAM530qE1Wzc0Ndwo6DLE805/dL8XhvG0n0QwF5TGo1SEfQw6nc7gRs QrrNEuQnig5rLnn4+8uSMZtDnYwFFZlS9cdtfUhijgJsS4KAj/EUXV2Yz9ERVaddw5L1yaxb61F DXOIewaGozO5FjHsyUCMo8kn4 X-Received: by 2002:aa7:d79a:: with SMTP id s26mr691036edq.202.1590664441905; Thu, 28 May 2020 04:14:01 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwcIxMeWbuUuJrdgZ6nC5IX8oVcCIpZYD5OLHWNuGYJPlq8iLJvJHCCYGlH5ttb3a/cZT7dUw== X-Received: by 2002:aa7:d79a:: with SMTP id s26mr691015edq.202.1590664441737; Thu, 28 May 2020 04:14:01 -0700 (PDT) Received: from vitty.brq.redhat.com (g-server-2.ign.cz. [91.219.240.2]) by smtp.gmail.com with ESMTPSA id cq27sm3509764edb.41.2020.05.28.04.14.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 May 2020 04:14:01 -0700 (PDT) From: Vitaly Kuznetsov To: Paolo Bonzini , kvm@vger.kernel.org, x86@kernel.org Cc: Andy Lutomirski , Thomas Gleixner , Borislav Petkov , "H. Peter Anvin" , Wanpeng Li , Sean Christopherson , Jim Mattson , Vivek Goyal , Gavin Shan , Peter Zijlstra , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 10/10] KVM: x86: deprecate KVM_ASYNC_PF_SEND_ALWAYS In-Reply-To: <551b75f7-b022-313d-fac4-8b3dd83fe76c@redhat.com> References: <20200525144125.143875-1-vkuznets@redhat.com> <20200525144125.143875-11-vkuznets@redhat.com> <551b75f7-b022-313d-fac4-8b3dd83fe76c@redhat.com> Date: Thu, 28 May 2020 13:14:00 +0200 Message-ID: <87zh9s2txj.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Paolo Bonzini writes: > On 25/05/20 16:41, Vitaly Kuznetsov wrote: >> Concerns were expressed around APF events delivery when CPU is not >> in user mode (KVM_ASYNC_PF_SEND_ALWAYS), e.g. >> https://lore.kernel.org/kvm/ed71d0967113a35f670a9625a058b8e6e0b2f104.1583547991.git.luto@kernel.org/ >> >> 'Page ready' events are already free from '#PF abuse' but 'page not ready' >> notifications still go through #PF (to be changed in the future). Make the >> probability of running into issues when APF collides with regular #PF lower >> by deprecating KVM_ASYNC_PF_SEND_ALWAYS. The feature doesn't seem to be >> important enough for any particular workload to notice the difference. > > This has been disabled already in guest code, but I don't see a > particular reason to deprecate it in the host too. Supporting it on the > host is just one line of code; if it's a problem *for the guest*, you > just don't use KVM_ASYNC_PF_SEND_ALWAYS. > > Also, note that #VE will always be delivered to the guest even at CPL0; > the decision on whether to do sync or async page fault at CPL0 will move > to the guest, but enabling #VE will probably _require_ the > KVM_ASYNC_PF_SEND_ALWAYS bit to be set (and KVM_ASYNC_PF_DELIVERY_AS_INT > as well). I actually missed the fact that guest side is already disabled (I can see it now in the queue), feel free to ignore this patch then. -- Vitaly