Hello,
I kind of ignored this feature when it was first announced. I assumed it was just for nested virtualization, and it does play a role in that.
But on further reading, it sounds like since it impacts the memory mapping of VFIO devices, it has performance impacts for real PCIe devices passed through to a VM? Is that right?
I know that performance improvements can't be gauranteed, but adding some examples of potential performance boosts to the docs, or more broadly a section on when/why/what use cases you'd want to enable it might be useful.
See: https://pve.proxmox.com/pve-docs/pve-admin-guide.html#qm_pci_viommu
Also, the docs seem to suggest that Intel's vIOMMU implementation is older and less featureful compared to VirtIO vIOMMU, but Intel vIOMMU seems to be what everyone posting here is using. Is there a reason for that? Is Intel's implementation actually better for certain use cases, or is it the case that the VirtIO implementation is still more experimental?
@uzumo has been experimenting with VIOMMU with Intel iGPU SR-IOV-based passthrough; it got me curious and made me realize I didn't really understand it yet.
I kind of ignored this feature when it was first announced. I assumed it was just for nested virtualization, and it does play a role in that.
But on further reading, it sounds like since it impacts the memory mapping of VFIO devices, it has performance impacts for real PCIe devices passed through to a VM? Is that right?
I know that performance improvements can't be gauranteed, but adding some examples of potential performance boosts to the docs, or more broadly a section on when/why/what use cases you'd want to enable it might be useful.
See: https://pve.proxmox.com/pve-docs/pve-admin-guide.html#qm_pci_viommu
Also, the docs seem to suggest that Intel's vIOMMU implementation is older and less featureful compared to VirtIO vIOMMU, but Intel vIOMMU seems to be what everyone posting here is using. Is there a reason for that? Is Intel's implementation actually better for certain use cases, or is it the case that the VirtIO implementation is still more experimental?
@uzumo has been experimenting with VIOMMU with Intel iGPU SR-IOV-based passthrough; it got me curious and made me realize I didn't really understand it yet.
