Re: [pve-devel] [PATCH qemu-server v6 1/4] feature #3784: Parameter for guest vIOMMU & machine as property-string

[Thomas Lamprecht <t.lamprecht@proxmox.com>]

Am 22/08/2023 um 14:40 schrieb Markus Frank:
> vIOMMU enables the option to passthrough pci devices to L2 VMs
> in L1 VMs via Nested Virtualisation.
> 
> QEMU-Parameters:
> https://www.qemu.org/docs/master/system/qemu-manpage.html
> https://wiki.qemu.org/Features/VT-d
> 
> -machine ...,kernel-irqchip=split:
> 
> "split" because of intremap see below.
> 
> -device intel-iommu:
> 
> * caching-mode=on:
> 
> "It is required for -device vfio-pci to work with the VT-d device, because host
> assigned devices requires to setup the DMA mapping on the host before guest DMA
> starts."
> 
> * intremap=on:
> 
> "This enables interrupt remapping feature. It's required to enable complete
> x2apic. Currently it only supports kvm kernel-irqchip modes off or split, while
> full kernel-irqchip is not yet supported."


looks ok, but I'd like to have the format change and additions of helpers
infrastructure split from adding the "viommu" property.

I.e., first add only the format and default_key and change the call sites,
this should have no semantic effect at all.
Then add the "viommu" parameter to the new format and whatever it needs to
respect that, the latter could then be merged with the test patches.