[virtio-dev] RE: [PATCH 00/11] Introduce transitional mmr pci device

Parav Pandit
2023-04-03T15:48:03Z

> From: Michael S. Tsirkin <mst@redhat.com>
> Sent: Monday, April 3, 2023 11:34 AM

> Another is that we can actually work around legacy bugs in the hypervisor. For
> example, atomicity and alignment bugs do not exist under DMA. Consider MAC
> field, writeable in legacy. Problem this write is not atomic, so there is a window
> where MAC is corrupted. If you do MMIO then you just have to copy this bug.
> If you do DMA then hypervisor can buffer all of MAC and send to device in one
> go.
I am familiar with this bug.
Users feedback that we received so far has kernels with driver support that uses CVQ for setting the mac address on legacy device.
So, it may help but not super important.

Also, if I recollect correctly, the mac address is configuring bit early in if-scripts sequence before bringing up the interface.
So, haven't seen real issue around it.