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[79.176.44.197]) by smtp.gmail.com with ESMTPSA id q17sm10042wro.36.2020.12.02.14.00.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Dec 2020 14:00:25 -0800 (PST) Date: Wed, 2 Dec 2020 17:00:22 -0500 From: "Michael S. Tsirkin" To: Jason Wang Cc: Eli Cohen , Cindy Lu , virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] vdpa/mlx5: Use random MAC for the vdpa net instance Message-ID: <20201202165932-mutt-send-email-mst@kernel.org> References: <20201130035147-mutt-send-email-mst@kernel.org> <20201130092759.GB99449@mtl-vdi-166.wap.labs.mlnx> <20201130043050-mutt-send-email-mst@kernel.org> <20201130103142-mutt-send-email-mst@kernel.org> <20201202055714.GA224423@mtl-vdi-166.wap.labs.mlnx> <20201202041518-mutt-send-email-mst@kernel.org> <3e32ef6d-83c9-5866-30e5-f6eeacd5044d@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <3e32ef6d-83c9-5866-30e5-f6eeacd5044d@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 02, 2020 at 09:48:25PM +0800, Jason Wang wrote: > > On 2020/12/2 下午5:23, Michael S. Tsirkin wrote: > > On Wed, Dec 02, 2020 at 07:57:14AM +0200, Eli Cohen wrote: > > > On Wed, Dec 02, 2020 at 12:18:36PM +0800, Jason Wang wrote: > > > > On 2020/12/1 下午5:23, Cindy Lu wrote: > > > > > On Mon, Nov 30, 2020 at 11:33 PM Michael S. Tsirkin wrote: > > > > > > On Mon, Nov 30, 2020 at 06:41:45PM +0800, Cindy Lu wrote: > > > > > > > On Mon, Nov 30, 2020 at 5:33 PM Michael S. Tsirkin wrote: > > > > > > > > On Mon, Nov 30, 2020 at 11:27:59AM +0200, Eli Cohen wrote: > > > > > > > > > On Mon, Nov 30, 2020 at 04:00:51AM -0500, Michael S. Tsirkin wrote: > > > > > > > > > > On Mon, Nov 30, 2020 at 08:27:46AM +0200, Eli Cohen wrote: > > > > > > > > > > > On Sun, Nov 29, 2020 at 03:08:22PM -0500, Michael S. Tsirkin wrote: > > > > > > > > > > > > On Sun, Nov 29, 2020 at 08:43:51AM +0200, Eli Cohen wrote: > > > > > > > > > > > > > We should not try to use the VF MAC address as that is used by the > > > > > > > > > > > > > regular (e.g. mlx5_core) NIC implementation. Instead, use a random > > > > > > > > > > > > > generated MAC address. > > > > > > > > > > > > > > > > > > > > > > > > > > Suggested by: Cindy Lu > > > > > > > > > > > > > Fixes: 1a86b377aa21 ("vdpa/mlx5: Add VDPA driver for supported mlx5 devices") > > > > > > > > > > > > > Signed-off-by: Eli Cohen > > > > > > > > > > > > I didn't realise it's possible to use VF in two ways > > > > > > > > > > > > with and without vdpa. > > > > > > > > > > > Using a VF you can create quite a few resources, e.g. send queues > > > > > > > > > > > recieve queues, virtio_net queues etc. So you can possibly create > > > > > > > > > > > several instances of vdpa net devices and nic net devices. > > > > > > > > > > > > > > > > > > > > > > > Could you include a bit more description on the failure > > > > > > > > > > > > mode? > > > > > > > > > > > Well, using the MAC address of the nic vport is wrong since that is the > > > > > > > > > > > MAC of the regular NIC implementation of mlx5_core. > > > > > > > > > > Right but ATM it doesn't coexist with vdpa so what's the problem? > > > > > > > > > > > > > > > > > > > This call is wrong: mlx5_query_nic_vport_mac_address() > > > > > > > > > > > > > > > > > > > > > Is switching to a random mac for such an unusual > > > > > > > > > > > > configuration really justified? > > > > > > > > > > > Since I can't use the NIC's MAC address, I have two options: > > > > > > > > > > > 1. To get the MAC address as was chosen by the user administering the > > > > > > > > > > > NIC. This should invoke the set_config callback. Unfortunately this > > > > > > > > > > > is not implemented yet. > > > > > > > > > > > > > > > > > > > > > > 2. Use a random MAC address. This is OK since if (1) is implemented it > > > > > > > > > > > can always override this random configuration. > > > > > > > > > > > > > > > > > > > > > > > It looks like changing a MAC could break some guests, > > > > > > > > > > > > can it not? > > > > > > > > > > > > > > > > > > > > > > > No, it will not. The current version of mlx5 VDPA does not allow regular > > > > > > > > > > > NIC driver and VDPA to co-exist. I have patches ready that enable that > > > > > > > > > > > from steering point of view. I will post them here once other patches on > > > > > > > > > > > which they depend will be merged. > > > > > > > > > > > > > > > > > > > > > > https://patchwork.ozlabs.org/project/netdev/patch/20201120230339.651609-12-saeedm@nvidia.com/ > > > > > > > > > > Could you be more explicit on the following points: > > > > > > > > > > - which configuration is broken ATM (as in, two device have identical > > > > > > > > > > macs? any other issues)? > > > > > > > > > The only wrong thing is the call to mlx5_query_nic_vport_mac_address(). > > > > > > > > > It's not breaking anything yet is wrong. The random MAC address setting > > > > > > > > > is required for the steering patches. > > > > > > > > Okay so I'm not sure the Fixes tag at least is appropriate if it's a > > > > > > > > dependency of a new feature. > > > > > > > > > > > > > > > > > > - why won't device MAC change from guest point of view? > > > > > > > > > > > > > > > > > > > It's lack of implementation in qemu as far as I know. > > > > > > > > Sorry not sure I understand. What's not implemented in QEMU? > > > > > > > > > > > > > > > HI Michael, there are some bug in qemu to set_config, this will fix in future, > > > > > > > But this patch is still needed, because without this patch the mlx > > > > > > > driver will give an 0 mac address to qemu > > > > > > > and qemu will overwrite the default mac address. This will cause traffic down. > > > > > > Hmm the patch description says VF mac address, not 0 address. Confused. > > > > > > If there's no mac we can clear VIRTIO_NET_F_MAC and have guest > > > > > > use a random value ... > > > > I'm not sure this can work for all types of vDPA (e.g it could not be a > > > > learning bridge in the swtich). > > > > > > > > > > > > > hi Michael， > > > > > I have tried as your suggestion, seems even remove the > > > > > VIRTIO_NET_F_MAC the qemu will still call get_cinfig and overwrite the > > > > > default address in VM, > > > > This looks a bug in qemu, in guest driver we had: > > > > > > > >     /* Configuration may specify what MAC to use.  Otherwise random. */ > > > >     if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC)) > > > >         virtio_cread_bytes(vdev, > > > >                    offsetof(struct virtio_net_config, mac), > > > >                    dev->dev_addr, dev->addr_len); > > > >     else > > > >         eth_hw_addr_random(dev); > > > > > > > > > > > > > this process is like > > > > > vdpa _init -->qemu call get_config ->mlx driver will give an mac > > > > > address with all 0--> > > > > > qemu will not check this mac address and use it --> overwrite the mac > > > > > address in qemu > > > > > > > > > > So for my understanding there are several method to fix this problem > > > > > > > > > > 1, qemu check the mac address, if the mac address is all 0, qemu will > > > > > ignore it and set the random mac address to mlx driver. > > > > So my understanding is that, if mac address is all 0, vDPA parent should not > > > > advertise VIRTIO_NET_F_MAC. And qemu should emulate this feature as you did: > > > Thinking it over, at least in mlx5, I should always advertise > > > VIRTIO_NET_F_MAC and set a non zero MAC value. The source of the MAC can > > > be either randomly generated value by mlx5_vdpa or by a management tool. > > > This is important becauase we should not let the VM modify the MAC. If > > > we do it can set a MAC value identical to the mlx5 NIC driver and can > > > kidnap traffic that was not destined to it. > > > > > > In addition, when VIRTIO_NET_F_MAC is published, attempts to change the > > > MAC address from the VM should result in error. > > That is not what the spec says though. > > VIRTIO_NET_F_MAC only says whether mac is valid in the config space. > > Whether guest can control that depends on VIRTIO_NET_F_CTRL_MAC_ADDR: > > > > The VIRTIO_NET_CTRL_MAC_ADDR_SET command is used to set the default MAC address which rx > > filtering accepts (and if VIRTIO_NET_F_MAC_ADDR has been negotiated, this will be reflected in mac in > > config space). > > The command-specific-data for VIRTIO_NET_CTRL_MAC_ADDR_SET is the 6-byte MAC address. > > > Consider VIRTIO_NET_CTRL_MAC_ADDR_SET is not supported now. What Eli > proposed here should work? > > Thanks > We can have management set a MAC address. Randomizing it in kernel does not seem like a reasonable policy to me ... > > > > > > > >