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. Thanks, Dragos
