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[79.176.44.197]) by smtp.gmail.com with ESMTPSA id q4sm3852657wmc.2.2020.11.30.07.30.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 30 Nov 2020 07:30:45 -0800 (PST) Date: Mon, 30 Nov 2020 10:30:42 -0500 From: "Michael S. Tsirkin" To: Eli Cohen Cc: jasowang@redhat.com, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, lulu@redhat.com Subject: Re: [PATCH] vdpa/mlx5: Use random MAC for the vdpa net instance Message-ID: <20201130102633-mutt-send-email-mst@kernel.org> References: <20201129064351.63618-1-elic@nvidia.com> <20201129150505-mutt-send-email-mst@kernel.org> <20201130062746.GA99449@mtl-vdi-166.wap.labs.mlnx> <20201130035147-mutt-send-email-mst@kernel.org> <20201130092759.GB99449@mtl-vdi-166.wap.labs.mlnx> <20201130043050-mutt-send-email-mst@kernel.org> <20201130115106.GC99449@mtl-vdi-166.wap.labs.mlnx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201130115106.GC99449@mtl-vdi-166.wap.labs.mlnx> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 30, 2020 at 01:51:06PM +0200, Eli Cohen wrote: > On Mon, Nov 30, 2020 at 04:33:09AM -0500, 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. > > > > OK, let's leave it for now. I will push along with the steering patches. > The meaning is the the VDPA net device instance is create with a MAC of > all zeros which also mean the link is down. You can set a MAC which will > let the link come up. > The vdpa driver will not get a callback as I > stated but since current mode of steering directs all traffic to the > vdpa instance it will work. In the future this must be fixed. So at the moment the MAC is in the config space and that is read during probe. So I guess userspace will do that before passing device to guest. > > > > > - 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? > > > > vdpa config operation set_config() should be called whenever the MAC is > changed, e.g. when administrator of the vdpa net device changes the mac. > This does not happen which is a bug. I am not sure that's a good interface for that, I think set_config is for guest writes into config space. Will let Jason comment once patches are posted. > > > > > > > > > > > --- > > > > > > > drivers/vdpa/mlx5/net/mlx5_vnet.c | 5 +---- > > > > > > > 1 file changed, 1 insertion(+), 4 deletions(-) > > > > > > > > > > > > > > diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c > > > > > > > index 1fa6fcac8299..80d06d958b8b 100644 > > > > > > > --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c > > > > > > > +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c > > > > > > > @@ -1955,10 +1955,7 @@ void *mlx5_vdpa_add_dev(struct mlx5_core_dev *mdev) > > > > > > > if (err) > > > > > > > goto err_mtu; > > > > > > > > > > > > > > - err = mlx5_query_nic_vport_mac_address(mdev, 0, 0, config->mac); > > > > > > > - if (err) > > > > > > > - goto err_mtu; > > > > > > > - > > > > > > > + eth_random_addr(config->mac); > > > > > > > mvdev->vdev.dma_dev = mdev->device; > > > > > > > err = mlx5_vdpa_alloc_resources(&ndev->mvdev); > > > > > > > if (err) > > > > > > > -- > > > > > > > 2.26.2 > > > > > > > > > > > >