[pve-devel] [RFC qemu-server v2 4/4] machine: warn intel-iommu users about too large address width

[Fiona Ebner]

Am 02.09.25 um 1:23 PM schrieb Daniel Kral:
> Similarily to the guest address width exceeding the vIOMMU address
> width, also warn users about the Intel vIOMMU address width being larger
> than the maximum allowed value, the maximum guest address width, as
> reported by the hardware.
> 
> Signed-off-by: Daniel Kral <d.kral at proxmox.com>
> ---
> I only added this as it was relatively cheap to implement now, but the
> user will be stopped by starting the VM anyway by issuing something
> like:
> 
> kvm: -device vfio-pci,host=0000:00:02.0,id=hostpci0,bus=pci.0,addr=0x10:
>     vfio 0000:00:02.0: Failed to set vIOMMU: aw-bits 48 > host aw-bits 39

I feel like we don't gain much by having an additional warning here. The
error from QEMU is already rather clear IMHO. If it's still cheap after
deciding which way we go with patch qemu-server 3/4, then we can still
go for it, but the warning should mention what the user can do to fix
the issue.