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=-5.0 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 4F033C433DB for ; Thu, 11 Feb 2021 09:16:15 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C176F64DB1 for ; Thu, 11 Feb 2021 09:16:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C176F64DB1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:49204 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lA857-0005dU-TU for qemu-devel@archiver.kernel.org; Thu, 11 Feb 2021 04:16:13 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:44068) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lA83e-0004hb-Dd for qemu-devel@nongnu.org; Thu, 11 Feb 2021 04:14:42 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:55933) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1lA83c-0005vF-1B for qemu-devel@nongnu.org; Thu, 11 Feb 2021 04:14:42 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1613034878; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=SBo0hLEj0uXrptZWMoUzzBu3AME3rMHo55XokhUW1Bo=; b=PYnjXT+deCZVwc1E5KyZCd394sFhyBrH9ckIjmfDNVoSCW556r2P9FrpAqR3QdatXTPz+G O3sLRxllQfrPumLOks56wftIiAP7NtlZsyvlpNdUh8rHnTay6jHKRMs6HHDLyhz2lRhifT eb5IMD7kT8L0qsjC8KD+qnwZvphB/BY= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-516-qzRlXIJZNuyUJfqVRdsldA-1; Thu, 11 Feb 2021 04:14:36 -0500 X-MC-Unique: qzRlXIJZNuyUJfqVRdsldA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5F8E91005501 for ; Thu, 11 Feb 2021 09:14:35 +0000 (UTC) Received: from redhat.com (ovpn-114-239.ams2.redhat.com [10.36.114.239]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DEA3F60657; Thu, 11 Feb 2021 09:14:33 +0000 (UTC) Date: Thu, 11 Feb 2021 09:14:30 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Vitaly Kuznetsov Subject: Re: [PATCH v4 00/19] i386: KVM: expand Hyper-V features early and provide simple 'hv-default=on' option Message-ID: <20210211091430.GB1302824@redhat.com> References: <20210210164033.607612-1-vkuznets@redhat.com> <20210210165606.GM1240644@redhat.com> <20210210174652.GE1420762@habkost.net> <87ft23m2f6.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 In-Reply-To: <87ft23m2f6.fsf@vitty.brq.redhat.com> User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -33 X-Spam_score: -3.4 X-Spam_bar: --- X-Spam_report: (-3.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.568, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Paolo Bonzini , Igor Mammedov , Marcelo Tosatti , Eduardo Habkost , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Feb 11, 2021 at 09:30:53AM +0100, Vitaly Kuznetsov wrote: > Eduardo Habkost writes: > > > On Wed, Feb 10, 2021 at 04:56:06PM +0000, Daniel P. Berrangé wrote: > >> On Wed, Feb 10, 2021 at 05:40:12PM +0100, Vitaly Kuznetsov wrote: > >> > Changes since v3: > >> > - Make 'hv-default' override 'hv-*' options which were already set > >> > (e.g. 'hv-feature=on,hv-default' case) [Igor]. Make 'hv-passthrough' > >> > behave the same way. > >> > - Add "i386: be more picky about implicit 'hv-evmcs' enablement" patch to avoid > >> > enabling 'hv-evmcs' with hv-default/hv-passthrough when guest CPU lacks VMX. > >> > - Add "i386: support 'hv-passthrough,hv-feature=off' on the command line" patch > >> > to make 'hv-passthrough' semantics match the newly introduced 'hv-default'. > >> > - Add "i386: track explicit 'hv-*' features enablement/disablement" patch to > >> > support the above mentioned changes. > >> > - Expand qtest to check the above mentioned improvements. > >> > > >> > Original description: > >> > > >> > Upper layer tools like libvirt want to figure out which Hyper-V features are > >> > supported by the underlying stack (QEMU/KVM) but currently they are unable to > >> > do so. We have a nice 'hv_passthrough' CPU flag supported by QEMU but it has > >> > no effect on e.g. QMP's > >> > > >> > query-cpu-model-expansion type=full model={"name":"host","props":{"hv-passthrough":true}} > >> > > >> > command as we parse Hyper-V features after creating KVM vCPUs and not at > >> > feature expansion time. To support the use-case we first need to make > >> > KVM_GET_SUPPORTED_HV_CPUID ioctl a system-wide ioctl as the existing > >> > vCPU version can't be used that early. This is what KVM part does. With > >> > that done, we can make early Hyper-V feature expansion (this series). > >> > > >> > In addition, provide a simple 'hv-default' option which enables (and > >> > requires from KVM) all currently supported Hyper-V enlightenments. > >> > Unlike 'hv-passthrough' mode, this is going to be migratable. > >> > >> How is it going to be migratable if the semantics vary depending on > >> the host kernel KVM reporting features, because different kernels > >> will expose different features ? > > > > "all currently supported" in this context means "all features > > supported when the machine type was added", not "all features > > supported by the host kernel". > > Yes, exactly. > > 'hv-passthrough' enables 'everything supported by the host' and this is > not migratable. > > 'hv-default' requires a certain set of features (depending on the > machine type) so the VM won't start if the host lacks something. Ok, so I presume HV features will only be added to hv-default when we know they are available in the oldest kernel we are targetting ? Upsteam is more conservative in this respect than downstreams, the latter can guarantee much more modern kernels. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|