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However, this >>>>>>>>>>> address can be 0 which prevents the driver from properly >>>>>>>>>>> configuring the MPFS and breaks steering. >>>>>>>>>>> >>>>>>>>>>> The solution is to simply generate a random MAC address >>>>>>>>>>> when no MAC is set on the nic vport. >>>>>>>>>>> >>>>>>>>>>> Now it's possible to create a vdpa device without a >>>>>>>>>>> MAC address and run qemu with this device without needing >>>>>>>>>>> to configure an explicit MAC address. >>>>>>>>>>> >>>>>>>>>>> Signed-off-by: Dragos Tatulea >>>>>>>>>>> Reviewed-by: Jiri Pirko >>>>>>>>>> >>>>>>>>>> Acked-by: Jason Wang >>>>>>>>>> >>>>>>>>>> (Adding Cindy for double checking if it has any side effect on Qemu side) >>>>>>>>>> >>>>>>>>>> Thanks >>>>>>>>>> >>>>>>>>> But Now there is a bug in QEMU: if the hardware MAC address does not >>>>>>>>> match the one in the QEMU command line, it will cause traffic loss. >>>>>>>>> >>>>>>>> Why is this a new issue in qemu? qemu in it's current state won't work >>>>>>>> with a different mac address that the one that is set in HW anyway. >>>>>>>> >>>>>>> this is not a new bug. We are trying to fix it because it will cause >>>>>>> traffic lose without any warning. >>>>>>> in my fix , this setting (different mac in device and Qemu) will fail >>>>>>> to load the VM. >>>>>> Which is a good thing, right? Some feedback to the user that there is >>>>>> a misconfig. I got bitten by this so many times... Thank you for adding it. >>>>>> >>>>>>> >>>>>>>>> So, Just an FYI here: if your patch merged, it may cause traffic loss. >>>>>>>>> and now I'm working in the fix it in qemu, the link is >>>>>>>>> https://patchew.org/QEMU/20240716011349.821777-1-lulu@redhat.com/ >>>>>>>>> The idea of this fix is >>>>>>>>> There are will only two acceptable situations for qemu: >>>>>>>>> 1. The hardware MAC address is the same as the MAC address specified >>>>>>>>> in the QEMU command line, and both MAC addresses are not 0. >>>>>>>>> 2. The hardware MAC address is not 0, and the MAC address in the QEMU >>>>>>>>> command line is 0. In this situation, the hardware MAC address will >>>>>>>>> overwrite the QEMU command line address. >>>>>>>>> >>>>>>>> Why would this not work with this patch? This patch simply sets a MAC >>>>>>>> if the vport doesn't have one set. Which allows for more scenarios to >>>>>>>> work. >>>>>>>> >>>>>>> I do not mean your patch will not work, I just want to make some >>>>>>> clarify here.Your patch + my fix may cause the VM to fail to load in >>>>>>> some situations, and this is as expected. >>>>>>> Your patch is good to merge. >>>>>> Ack. Thank you for the clarification. >>>>>> >>>>>> Thanks, >>>>>> Dragos >>>>>> >>>>> Hi Dragos， >>>>> I think we need to hold this patch. Because it may not be working >>>>> with upstream qemu. >>>>> >>>>> MLX will create a random MAC address for your patch. Additionally, if >>>>> there is no specific MAC in the QEMU command line, QEMU will also >>>>> generate a random MAC. >>>>> these two MAC are not the same. and this will cause traffic loss. >>>> Ahaa, it turns out that qemu 8.x and 9.x have different behaviour. >>>> >>>> Initially I was testing this scenario (vdpa device created with no mac >>>> and no mac set in qemu cli) with qemu 8.x. There, qemu was not being >>>> able to set the qemu generated random mac addres because .set_config() >>>> is a nop in mlx5_vdpa. >>>> >>>> Then I moved to qemu 9.x and saw that this scenario was working because >>>> now the CVQ was used instead to configure the mac on the device. >>>> >>>> So this patch should definitely not be applied. >>>> >>>> I was thinking if there are ways to fix this for 8.x. The only feasible >>>> way is to implement .set_config() in mlx5_vdpa for the mac >>>> configuration. But as you previousy said, this is discouraged. >>>> >>> I just tested your referenced qemu fix from patchwork and I found that >>> for the case when a vdpa device doesn't have a mac address (mac address >>> 0 and VIRTIO_NET_F_MAC not set) qemu will return an error. So with this >>> fix we'd be back to square one where the user always has to set a mac >>> somewhere. >>> >>> Would it be possible to take this case into consideration with your >>> fix? >>> >>> Thanks, >>> Dragos >>> >> Hi Dragos >> >> Thanks for your test and help, I think I can add a check for >> VIRTIO_NET_F_MAC in the qemu code. if the device's Mac is 0 and the >> VIRTIO_NET_F_MAC is not set. The guest VM will fail to load. I will >> double-check this > My request was to use the random MAC from qemu in this case. qemu is > able to configure the device via CVQ. At least this device... Also, it makes sense that if a device doesn't have a MAC set and VIRTIO_NET_F_CTRL_MAC_ADDR is set then qemu can set a random mac on that device. Thanks, Dragos