On 29.08.24 12:00, Dragos Tatulea wrote: > > > On 29.08.24 11:05, Cindy Lu wrote: >> On Wed, 28 Aug 2024 at 17:37, Dragos Tatulea <dtatulea@xxxxxxxxxx> wrote: >>> >>> >>> >>> On 28.08.24 11:00, Cindy Lu wrote: >>>> On Wed, 28 Aug 2024 at 09:51, Jason Wang <jasowang@xxxxxxxxxx> wrote: >>>>> >>>>> On Wed, Aug 28, 2024 at 12:03 AM Dragos Tatulea <dtatulea@xxxxxxxxxx> wrote: >>>>>> >>>>>> When the vdpa device is configured without a specific MAC >>>>>> address, the vport MAC address is used. 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 <dtatulea@xxxxxxxxxx> >>>>>> Reviewed-by: Jiri Pirko <jiri@xxxxxxxxxx> >>>>> >>>>> Acked-by: Jason Wang <jasowang@xxxxxxxxxx> >>>>> >>>>> (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@xxxxxxxxxx/ >>>> 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. (Side note) While looking at another issue I discovered that it's possible to configure a random MAC on the mlx5_vdpa device at VM boot time if device MAC configuration is implemented during during .set_config(). So I was able to boot up a VM with a random MAC address coming from qemu and the traffic worked with this new MAC. So now I'm not sure if this is just by luck or if the .set_config() op should be implemented for the MAC part in our device. Thanks, Dragos
