Started getting this warning on a VM where I pass through a SATA controller on proxmox 9.2.

[chrcoluk]

kvm: -device vfio-pci,host=0000:01:00.0,id=hostpci0,bus=pci.0,addr=0x10: warning: VFIO dma-buf not supported in kernel: PCI BAR IOMMU mappings may fail
TASK WARNINGS: 1

Only hit I can find on google is a recent about a month old post where someone is going to remove this warning from the kernel, and since the devices all work, am I right I can ignore this warning?

 

[celemine1gig]

And what exactly is the issue here? How often do you see this message? Why does it bother you?
As you might have already seen in your search, this start with kernels >v6.19.
However, from what I read, it is intended just to be that, a "warning", as one of the new features is not supported. So, unless this floods the logs, or leads to functional issues, I would recommend to ignore it.

 

[chrcoluk]

My search didnt reveal anything other than someone proposing to remove the warning from the kernel code. Nothing about the starting kernel version, although this is happening on 6.17 which is below 6.19.

If you do have more info I wouldnt mind a link thanks.

 

[celemine1gig]

The kernel version is irrelevant, if you answer none of the other questions.

Here is the exact code line where this is coming from:
https://github.com/qemu/qemu/blob/master/hw/vfio/region.c#L324

Same code is not included in QEMU 10.1:
https://github.com/qemu/qemu/blob/stable-10.1/hw/vfio/region.c

Honestly don't remember where I read about a corresponding kernel versions and I might be wrong anyway.
However, kernel-wise, the base support seems to have been added here:
https://git.kernel.org/pub/scm/linu...y&id=5d74781ebc86c5fa9e9d6934024c505412de9b52

 

[chrcoluk]

You didnt ask any other than what is the issue which is already mentioned in the OP.

There is no obvious operational issue, but it doesnt mean there isnt anything I havent noticed. I am not someone who just ignores warnings, unless I have enough knowledge of the warning to know its ok.

But thank you for the links. I always like to understand the reason for a warning.

If I understand right, the warning may go away if I revert back to the 7.0.x kernel. I am currently on 6.17.x, it looks like kernel support for dma-buf was added in 7.0.x.

 

[celemine1gig]

It might be, that feature compatability between QEMU and kernel version "causes" this message. That means one side trying to use a feature that the other cannot deal with. Easy to try out, if you are right with your assumption.
Looking forward to the result.