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=-20.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham 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 89560C433E0 for ; Wed, 3 Mar 2021 10:27:22 +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 B761F64E66 for ; Wed, 3 Mar 2021 10:27:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B761F64E66 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]:34176 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lHOiu-0006po-Lr for qemu-devel@archiver.kernel.org; Wed, 03 Mar 2021 05:27:20 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:37518) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lHOhp-00066J-Cu for qemu-devel@nongnu.org; Wed, 03 Mar 2021 05:26:13 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:46412) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1lHOhn-0004Tv-Kh for qemu-devel@nongnu.org; Wed, 03 Mar 2021 05:26:13 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1614767170; 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=nZm6pWmgh25+N5N3t2C+hGej2vVk/tx7tkvnzWFlt8k=; b=FZcmcmpdLFwcpPY492BNWxpB7cnTj7d9o8cqSxWngDczG6HPsVmQC8Tgg7tqbHle7aU63g b2dGIeWrh6zZcRnAqaLcMMQ/LCWaW5i2QW/9BLBgIsRj7CL0Rq4p+lFJ9Z0wwM/8VdZoCB dk3fauOeRCpudsdCwNGmJJsu/W3Tmww= 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-588-BeOsxT_oMxyzHm8DWK_Opg-1; Wed, 03 Mar 2021 05:26:09 -0500 X-MC-Unique: BeOsxT_oMxyzHm8DWK_Opg-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 11D53185A0CD; Wed, 3 Mar 2021 10:26:08 +0000 (UTC) Received: from [10.36.112.28] (ovpn-112-28.ams2.redhat.com [10.36.112.28]) by smtp.corp.redhat.com (Postfix) with ESMTP id ABA0B63633; Wed, 3 Mar 2021 10:26:03 +0000 (UTC) Subject: Re: [PATCH v1] vhost-vdpa: Set discarding of RAM broken when initializing the backend To: Jason Wang , qemu-devel@nongnu.org, Xie Yongji References: <20210302162129.52912-1-david@redhat.com> <81c675cd-1573-7555-7d20-07b0ed950ebb@redhat.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <886ed3b7-e48c-7200-e5e6-ce8b0adc589c@redhat.com> Date: Wed, 3 Mar 2021 11:26:02 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: <81c675cd-1573-7555-7d20-07b0ed950ebb@redhat.com> 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; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, 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: , Cc: Cindy Lu , "Michael S . Tsirkin" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 03.03.21 03:53, Jason Wang wrote: > > On 2021/3/3 12:21 上午, David Hildenbrand wrote: >> Similar to VFIO, vDPA will go ahead an map+pin all guest memory. Memory >> that used to be discarded will get re-populated and if we >> discard+re-access memory after mapping+pinning, the pages mapped into the >> vDPA IOMMU will go out of sync with the actual pages mapped into the user >> space page tables. >> >> Set discarding of RAM broken such that: >> - virtio-mem and vhost-vdpa run mutually exclusive >> - virtio-balloon is inhibited and no memory discards will get issued >> >> In the future, we might be able to support coordinated discarding of RAM >> as used by virtio-mem and as planned for VFIO. >> >> Cc: Jason Wang >> Cc: Michael S. Tsirkin >> Cc: Cindy Lu >> Signed-off-by: David Hildenbrand > > > Acked-by: Jason Wang > > >> --- >> >> Note: I was not actually able to reproduce/test as I fail to get the >> vdpa_sim/vdpa_sim_net running on upstream Linux (whetever vdpa, vhost_vdpa, >> vdpa_sim, vdpa_sim_net modules I probe, and in which order, no vdpa devices >> appear under /sys/bus/vdpa/devices/ or /dev/). > > > The device creation was switched to use vdpa tool that is integrated > with iproue2[1]. > > [1] > https://git.kernel.org/pub/scm/network/iproute2/iproute2-next.git/commit/?id=143610383da51e1f868c6d5a2a5e2fb552293d18 It would be great to document that somewhere if not already done. I only found older RH documentations that were not aware of that. I'll give it a try - thanks! > > >> >> --- >> hw/virtio/vhost-vdpa.c | 13 +++++++++++++ >> 1 file changed, 13 insertions(+) >> >> diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c >> index 01d2101d09..86058d4041 100644 >> --- a/hw/virtio/vhost-vdpa.c >> +++ b/hw/virtio/vhost-vdpa.c >> @@ -278,6 +278,17 @@ static int vhost_vdpa_init(struct vhost_dev *dev, void *opaque) >> uint64_t features; >> assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_VDPA); >> trace_vhost_vdpa_init(dev, opaque); >> + int ret; >> + >> + /* >> + * Similar to VFIO, we end up pinning all guest memory and have to >> + * disable discarding of RAM. >> + */ >> + ret = ram_block_discard_disable(true); >> + if (ret) { >> + error_report("Cannot set discarding of RAM broken"); >> + return ret; >> + } > > > vDPA will support non pinning (shared VM) backend soon[2]. So I guess we > need a flag to be advertised to usersapce then we can conditionly enable > the discard here. I thought that was already the default (because I stumbled over enforcing guest IOMMU) but was surprised when I had a look at the implementation. Having a flag sounds good. BTW: I assume iommu support is not fully working yet, right? I don't see special casing for iommu regions, including registering the listener and updating the mapping. -- Thanks, David / dhildenb