On Fri, 30 Aug 2024 at 03:03, Dragos Tatulea <dtatulea@xxxxxxxxxx> wrote: > > > > 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 > Hi Dragos， For qemu part, I think this is not set from set_config()? it should be from the CVQ? Usually, we don't recommend using the set_config() function because the configuration space should be read-only for modern devices. Now there is a bug in this part of qemu, and we plan to remove the code to set_config() in virtio_net_device_realize(), here is the patch https://lore.kernel.org/all/CACGkMEvCSKfahpBQLAMmSzdFN-QPhg5Zx+UQVrFX0HsWybZZNA@xxxxxxxxxxxxxx/T/ and this is still under review thanks cindy
