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Wed, 27 Jul 2022 08:44:05 -0700 (PDT) X-Google-Smtp-Source: AGRyM1uFZGQD3a281tjE4wzKhXvbtnkIpRIqZTMJS8oOccdgxgUCZ2E8X7qMw1LXWcjb+xYUX+5jGg== X-Received: by 2002:a17:907:9810:b0:72f:36e5:266c with SMTP id ji16-20020a170907981000b0072f36e5266cmr17963152ejc.105.1658936644855; Wed, 27 Jul 2022 08:44:04 -0700 (PDT) Received: from redhat.com ([2.52.132.243]) by smtp.gmail.com with ESMTPSA id g16-20020a50ee10000000b0043cc58ca84dsm796262eds.39.2022.07.27.08.44.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 27 Jul 2022 08:44:04 -0700 (PDT) Date: Wed, 27 Jul 2022 11:44:00 -0400 From: "Michael S. Tsirkin" To: Eli Cohen Subject: Re: VIRTIO_NET_F_MTU not negotiated Message-ID: <20220727114228-mutt-send-email-mst@kernel.org> References: <20220727032334-mutt-send-email-mst@kernel.org> <20220727053311-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: Eugenio Perez Martin , "qemu-devel@nongnu.org" , "virtualization@lists.linux-foundation.org" X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On Wed, Jul 27, 2022 at 10:16:19AM +0000, Eli Cohen wrote: > > -----Original Message----- > > From: Michael S. Tsirkin > > Sent: Wednesday, July 27, 2022 12:35 PM > > To: Eli Cohen > > Cc: Eugenio Perez Martin ; qemu-devel@nongnu.org; Jason Wang ; > > virtualization@lists.linux-foundation.org > > Subject: Re: VIRTIO_NET_F_MTU not negotiated > > > > On Wed, Jul 27, 2022 at 09:04:47AM +0000, Eli Cohen wrote: > > > > -----Original Message----- > > > > From: Michael S. Tsirkin > > > > Sent: Wednesday, July 27, 2022 10:25 AM > > > > To: Eli Cohen > > > > Cc: Eugenio Perez Martin ; qemu-devel@nongnu.org; Jason Wang ; > > > > virtualization@lists.linux-foundation.org > > > > Subject: Re: VIRTIO_NET_F_MTU not negotiated > > > > > > > > On Wed, Jul 27, 2022 at 06:51:56AM +0000, Eli Cohen wrote: > > > > > I found out that the reason why I could not enforce the mtu stems from the fact that I did not configure max mtu for the net > > device > > > > (e.g. through libvirt ). > > > > > Libvirt does not allow this configuration for vdpa devices and probably for a reason. The vdpa backend driver has the freedom > > to do > > > > it using its copy of virtio_net_config. > > > > > > > > > > The code in qemu that is responsible to allow to consider the device MTU restriction is here: > > > > > > > > > > static void virtio_net_device_realize(DeviceState *dev, Error **errp) > > > > > { > > > > > VirtIODevice *vdev = VIRTIO_DEVICE(dev); > > > > > VirtIONet *n = VIRTIO_NET(dev); > > > > > NetClientState *nc; > > > > > int i; > > > > > > > > > > if (n->net_conf.mtu) { > > > > > n->host_features |= (1ULL << VIRTIO_NET_F_MTU); > > > > > } > > > > > > > > > > The above code can be interpreted as follows: > > > > > if the command line arguments of qemu indicates that mtu should be limited, then we would read this mtu limitation from the > > > > device (that actual value is ignored). > > > > > > > > > > I worked around this limitation by unconditionally setting VIRTIO_NET_F_MTU in the host features. As said, it only indicates > > that > > > > we should read the actual limitation for the device. > > > > > > > > > > If this makes sense I can send a patch to fix this. > > > > > > > > Well it will then either have to be for vdpa only, or have > > > > compat machinery to avoid breaking migration. > > > > > > > > > > How about this one: > > > > > > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c > > > index 1067e72b3975..e464e4645c79 100644 > > > --- a/hw/net/virtio-net.c > > > +++ b/hw/net/virtio-net.c > > > @@ -3188,6 +3188,7 @@ static void virtio_net_guest_notifier_mask(VirtIODevice *vdev, int idx, > > > static void virtio_net_set_config_size(VirtIONet *n, uint64_t host_features) > > > { > > > virtio_add_feature(&host_features, VIRTIO_NET_F_MAC); > > > + virtio_add_feature(&host_features, VIRTIO_NET_F_MTU); > > > > > > n->config_size = virtio_feature_get_config_size(feature_sizes, > > > host_features); > > > > Seems to increase config size unconditionally? > > Right but you pay for reading two more bytes. Is that such a high price to pay? That's not a performance question. The issue compatibility, size should not change for a given machine type. > > > > > @@ -3512,6 +3513,7 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp) > > > > > > if (nc->peer && nc->peer->info->type == NET_CLIENT_DRIVER_VHOST_VDPA) { > > > struct virtio_net_config netcfg = {}; > > > + n->host_features |= (1ULL << VIRTIO_NET_F_MTU); > > > memcpy(&netcfg.mac, &n->nic_conf.macaddr, ETH_ALEN); > > > vhost_net_set_config(get_vhost_net(nc->peer), > > > (uint8_t *)&netcfg, 0, ETH_ALEN, VHOST_SET_CONFIG_TYPE_MASTER); > > > > And the point is vdpa does not support migration anyway ATM, right? > > > > I don't see how this can affect vdpa live migration. Am I missing something? config size affects things like pci BAR size. This must not change during migration. -- MST _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization 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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id A3217C19F2B for ; Wed, 27 Jul 2022 15:47:12 +0000 (UTC) Received: from localhost ([::1]:37404 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oGjFf-0000xO-Ho for qemu-devel@archiver.kernel.org; Wed, 27 Jul 2022 11:47:11 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:42918) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oGjCl-0007Hk-Cr for qemu-devel@nongnu.org; Wed, 27 Jul 2022 11:44:11 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:57208) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oGjCi-0007sJ-GJ for qemu-devel@nongnu.org; Wed, 27 Jul 2022 11:44:10 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1658936647; 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=Xjoftw+lPi/Jdd4dOQv7y6H1hb7jKnp8oUGe5twN9uw=; b=ROXneAvBvvsteAFiHIdqI2QhyasWaDGyon5ta9QRDaUkJkZlab7EDdPx2SAFJqlPZh0h8z PSt+8IOdEc+rbHSjdDW05TdMjKaTAaF5QJs1hCdk7JYtRm3NStODkMJ/wtCYu8xAjmzCMO QKzHoLNVtwDlNZKsBob387oXolGuNOM= Received: from mail-ed1-f70.google.com (mail-ed1-f70.google.com [209.85.208.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-78-fPezSYlIOs6QhWeuG-M0_A-1; Wed, 27 Jul 2022 11:44:06 -0400 X-MC-Unique: fPezSYlIOs6QhWeuG-M0_A-1 Received: by mail-ed1-f70.google.com with SMTP id o2-20020a056402438200b0043ccb3ed7dfso586666edc.22 for ; Wed, 27 Jul 2022 08:44:06 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc; bh=Xjoftw+lPi/Jdd4dOQv7y6H1hb7jKnp8oUGe5twN9uw=; b=Oo9703TlrJgmbu4lWBLWq0rhkxe/W3rlyvhyMeIZLk2mr7n1Gtlr6VDEzubUDHd66+ doWdxm8ZAqSDFvZDkajY3igcV5kyyzQ59NzdGJnApN6c9ZBUq4pzHkTFsnspKHl8okZB 9SN/zlkf5SoJgQlN8gl7Wf/G8eFSC4hRtDCguPoIBq05pXmPPybNkU7DKTc5WqYmYQ3g 5kAlR7l0VAY6RiM99Lu1/V2lDZbCyxCLeP2vqryVac5hHOG4N+pAiaDR+cxKdh3xwbKC EzOa95o44rWay1t3sg1uWuYRa5Y+ZQcPK4W4fsCWAwz7td+6MgNgFA82vrki8CrIwEep GiHg== X-Gm-Message-State: AJIora9JPqA0aKIPbL1BvaICAasLvDpVmLLLTvnABKXl2pD4YbAe/l7i SPe0OBrGe7RBMIkmrHgerC/AjA9/A33f7qVn7qHyRl3EkWhNXMzj/YUatjH8JtvyKek4yeGZQco 7gKffuZKz2+UbWrk= X-Received: by 2002:a17:907:9810:b0:72f:36e5:266c with SMTP id ji16-20020a170907981000b0072f36e5266cmr17963167ejc.105.1658936645138; Wed, 27 Jul 2022 08:44:05 -0700 (PDT) X-Google-Smtp-Source: AGRyM1uFZGQD3a281tjE4wzKhXvbtnkIpRIqZTMJS8oOccdgxgUCZ2E8X7qMw1LXWcjb+xYUX+5jGg== X-Received: by 2002:a17:907:9810:b0:72f:36e5:266c with SMTP id ji16-20020a170907981000b0072f36e5266cmr17963152ejc.105.1658936644855; Wed, 27 Jul 2022 08:44:04 -0700 (PDT) Received: from redhat.com ([2.52.132.243]) by smtp.gmail.com with ESMTPSA id g16-20020a50ee10000000b0043cc58ca84dsm796262eds.39.2022.07.27.08.44.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 27 Jul 2022 08:44:04 -0700 (PDT) Date: Wed, 27 Jul 2022 11:44:00 -0400 From: "Michael S. Tsirkin" To: Eli Cohen Cc: Eugenio Perez Martin , "qemu-devel@nongnu.org" , Jason Wang , "virtualization@lists.linux-foundation.org" Subject: Re: VIRTIO_NET_F_MTU not negotiated Message-ID: <20220727114228-mutt-send-email-mst@kernel.org> References: <20220727032334-mutt-send-email-mst@kernel.org> <20220727053311-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Received-SPF: pass client-ip=170.10.133.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Jul 27, 2022 at 10:16:19AM +0000, Eli Cohen wrote: > > -----Original Message----- > > From: Michael S. Tsirkin > > Sent: Wednesday, July 27, 2022 12:35 PM > > To: Eli Cohen > > Cc: Eugenio Perez Martin ; qemu-devel@nongnu.org; Jason Wang ; > > virtualization@lists.linux-foundation.org > > Subject: Re: VIRTIO_NET_F_MTU not negotiated > > > > On Wed, Jul 27, 2022 at 09:04:47AM +0000, Eli Cohen wrote: > > > > -----Original Message----- > > > > From: Michael S. Tsirkin > > > > Sent: Wednesday, July 27, 2022 10:25 AM > > > > To: Eli Cohen > > > > Cc: Eugenio Perez Martin ; qemu-devel@nongnu.org; Jason Wang ; > > > > virtualization@lists.linux-foundation.org > > > > Subject: Re: VIRTIO_NET_F_MTU not negotiated > > > > > > > > On Wed, Jul 27, 2022 at 06:51:56AM +0000, Eli Cohen wrote: > > > > > I found out that the reason why I could not enforce the mtu stems from the fact that I did not configure max mtu for the net > > device > > > > (e.g. through libvirt ). > > > > > Libvirt does not allow this configuration for vdpa devices and probably for a reason. The vdpa backend driver has the freedom > > to do > > > > it using its copy of virtio_net_config. > > > > > > > > > > The code in qemu that is responsible to allow to consider the device MTU restriction is here: > > > > > > > > > > static void virtio_net_device_realize(DeviceState *dev, Error **errp) > > > > > { > > > > > VirtIODevice *vdev = VIRTIO_DEVICE(dev); > > > > > VirtIONet *n = VIRTIO_NET(dev); > > > > > NetClientState *nc; > > > > > int i; > > > > > > > > > > if (n->net_conf.mtu) { > > > > > n->host_features |= (1ULL << VIRTIO_NET_F_MTU); > > > > > } > > > > > > > > > > The above code can be interpreted as follows: > > > > > if the command line arguments of qemu indicates that mtu should be limited, then we would read this mtu limitation from the > > > > device (that actual value is ignored). > > > > > > > > > > I worked around this limitation by unconditionally setting VIRTIO_NET_F_MTU in the host features. As said, it only indicates > > that > > > > we should read the actual limitation for the device. > > > > > > > > > > If this makes sense I can send a patch to fix this. > > > > > > > > Well it will then either have to be for vdpa only, or have > > > > compat machinery to avoid breaking migration. > > > > > > > > > > How about this one: > > > > > > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c > > > index 1067e72b3975..e464e4645c79 100644 > > > --- a/hw/net/virtio-net.c > > > +++ b/hw/net/virtio-net.c > > > @@ -3188,6 +3188,7 @@ static void virtio_net_guest_notifier_mask(VirtIODevice *vdev, int idx, > > > static void virtio_net_set_config_size(VirtIONet *n, uint64_t host_features) > > > { > > > virtio_add_feature(&host_features, VIRTIO_NET_F_MAC); > > > + virtio_add_feature(&host_features, VIRTIO_NET_F_MTU); > > > > > > n->config_size = virtio_feature_get_config_size(feature_sizes, > > > host_features); > > > > Seems to increase config size unconditionally? > > Right but you pay for reading two more bytes. Is that such a high price to pay? That's not a performance question. The issue compatibility, size should not change for a given machine type. > > > > > @@ -3512,6 +3513,7 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp) > > > > > > if (nc->peer && nc->peer->info->type == NET_CLIENT_DRIVER_VHOST_VDPA) { > > > struct virtio_net_config netcfg = {}; > > > + n->host_features |= (1ULL << VIRTIO_NET_F_MTU); > > > memcpy(&netcfg.mac, &n->nic_conf.macaddr, ETH_ALEN); > > > vhost_net_set_config(get_vhost_net(nc->peer), > > > (uint8_t *)&netcfg, 0, ETH_ALEN, VHOST_SET_CONFIG_TYPE_MASTER); > > > > And the point is vdpa does not support migration anyway ATM, right? > > > > I don't see how this can affect vdpa live migration. Am I missing something? config size affects things like pci BAR size. This must not change during migration. -- MST