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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... Thanks, Dragos