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Tsirkin" Cc: Cindy Lu , Eli Cohen , virtualization@lists.linux-foundation.org, linux-kernel@vger.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> <20201130103142-mutt-send-email-mst@kernel.org> <20201202042328-mutt-send-email-mst@kernel.org> From: Jason Wang Message-ID: <128487fe-8736-6d9e-3d07-b55dcb92c9b0@redhat.com> Date: Wed, 2 Dec 2020 20:56:37 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201202042328-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/12/2 下午5:30, Michael S. Tsirkin 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: >> >> 1) get a random mac > To me this looks like a spec violation. > > If the driver negotiates the VIRTIO_NET_F_MAC feature, the driver MUST set > the physical address of the NIC to \field{mac}. Otherwise, it SHOULD > use a locally-administered MAC address (see \hyperref[intro:IEEE 802]{IEEE 802}, > ``9.2 48-bit universal LAN MAC addresses''). One question here, what did "set" mean here consider the mac is given by the device itself? > > While not said explicitly, the assumption I think is that the local > MAC is not a local one. > > >> 2) advertise VIRTIO_NET_F_MAC >> 3) set the random mac to vDPA through set_config > that part looks wrong to me. Setting mac through set_config was > a pre-virtio-1.0 way to send mac to device. In 1.0 we have > VIRTIO_NET_CTRL_MAC_ADDR_SET for that: > > > When using the legacy interface, \field{mac} is driver-writable > which provided a way for drivers to update the MAC without > negotiating VIRTIO_NET_F_CTRL_MAC_ADDR. Looks like it doesn't prevent us from doing so. Otherwise this brings an implicit dependency for control virtqueue if we want to support 1.0? Thanks > > > >> 4) advertise the random mac to emulated config to guest >> >> >>> 2. mlx driver checks the mac address and if this mac is 0, return fail >>> to qemu, but this need to change the UAPI. >> >> uAPI is probably fine since ioctl can fail.  We can change the to allow the >> set_config to fail but virito spec doesn't have a way to advertise the error >> in this case. Anyway, the driver only risk itself for setting a wrong value, >> so we're probably fine. >> >> Thanks >> >> >>> 3. mlx driver it shelf should get an correct mac address while it init. >>> 4. add check in qemu get_config function , if there is not F_MAC Then >>> ignore the mac address from mlx driver >>> >>> not sure which method is more suitable ? >>> >>> Thanks >>> Cindy >>> >>> >>> >>>>>>>>>>> --- >>>>>>>>>>> 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