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=-5.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,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 EF3EBC433DB for ; Thu, 14 Jan 2021 16:36:08 +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 91651239FD for ; Thu, 14 Jan 2021 16:36:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 91651239FD 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]:49612 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l05bT-0001LB-Mq for qemu-devel@archiver.kernel.org; Thu, 14 Jan 2021 11:36:07 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:38586) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l05LK-000377-My for qemu-devel@nongnu.org; Thu, 14 Jan 2021 11:19:26 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:33395) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l05LI-0008S2-J1 for qemu-devel@nongnu.org; Thu, 14 Jan 2021 11:19:26 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1610641163; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=lVN3ipCxEMnAIof+8Lzo50Ao9LErZ/Z05KNGc522DBI=; b=c1KNHHXHyAesRvBMeSNN9NwKWEav+8ulxhvVlAmItET2XbWF8dPchqhtqsDPJKf9zm163P HzXTjWIrzA/sNFahObwPqOuw4XWwlE/8C96TtC4mg0xKHf0d+I+IgG6Kl6XWhWzPV65fr3 tncrQHggGXCyt058DLMDjLHojWjtVxo= 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-467-UPoULZ9-MtaEv1o04Q7zkA-1; Thu, 14 Jan 2021 11:19:22 -0500 X-MC-Unique: UPoULZ9-MtaEv1o04Q7zkA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7FADE8030A1; Thu, 14 Jan 2021 16:19:20 +0000 (UTC) Received: from [10.36.115.75] (ovpn-115-75.ams2.redhat.com [10.36.115.75]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6E2875D719; Thu, 14 Jan 2021 16:19:03 +0000 (UTC) Subject: Re: [PATCH v4 11/11] vfio: Disable only uncoordinated discards To: Alex Williamson References: <20210107133423.44964-1-david@redhat.com> <20210107133423.44964-12-david@redhat.com> <20210113165708.45a8701c@omen.home.shazbot.org> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: Date: Thu, 14 Jan 2021 17:19:02 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <20210113165708.45a8701c@omen.home.shazbot.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=david@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -32 X-Spam_score: -3.3 X-Spam_bar: --- X-Spam_report: (-3.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.248, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.237, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=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: , Cc: Marek Kedzierski , Pankaj Gupta , Wei Yang , "Michael S. Tsirkin" , qemu-devel@nongnu.org, Peter Xu , "Dr . David Alan Gilbert" , Auger Eric , Pankaj Gupta , teawater , Jonathan Cameron , Paolo Bonzini , Igor Mammedov Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 14.01.21 00:57, Alex Williamson wrote: > On Thu, 7 Jan 2021 14:34:23 +0100 > David Hildenbrand wrote: > >> We support coordinated discarding of RAM using the RamDiscardMgr. Let's >> unlock support for coordinated discards, keeping uncoordinated discards >> (e.g., via virtio-balloon) disabled. >> >> This unlocks virtio-mem + vfio. Note that vfio used via "nvme://" by the >> block layer has to be implemented/unlocked separately. For now, >> virtio-mem only supports x86-64 - spapr IOMMUs are not tested/affected. > > I think SPAPR always uses a vIOMMU, but I won't claim to understand it. I heard about that, but I also know that they are using virtio-balloon. Theoretically, virtio-balloon does currently not support vIOMMUs (iommu=on results in the balloon device essentially being disable). > Is there anything other than testing that restricts it to x86-64? ARM I am not aware, but well, I guess we'll learn as we go/unlock virtio-mem on these architectures. Jonathan is trying to enable arm64 support for virtio-mem. I asked him to test vfio. I'll have to cleanup my s390x prototype and find a machine to test with vfio. > and S390 will use the same type1 IOMMU backend as far as vfio support > is concerned. Should we do something more than put it in a commit log > if we really want to prevent it elsewhere? Thanks, I think it should be sufficient to have it in the logs for now. I'll be involved when unlocking virtio-mem on other archs and will request to test vfio. In case we find issues, we should try fixing them first (instead of fencing it / bailing out). Obviously, this won't stop other RamDiscardMgr users from popping up, but I guess we'll stumble over that as well. -- Thanks, David / dhildenb