https://blogs.damiendye.uk/en/series/pcie-passthrough-on-proxmox/ Recent content in PCIe Passthrough on Proxmox on Damien Dye's Blog Hugo en-GB Fri, 07 Aug 2026 10:00:00 +0100 https://blogs.damiendye.uk/en/proxmox/pcie-passthrough-performance-the-iommu-tax/ Fri, 07 Aug 2026 10:00:00 +0100 https://blogs.damiendye.uk/en/proxmox/pcie-passthrough-performance-the-iommu-tax/ Why PCIe devices lose throughput when passed through to a VM via VFIO, and the practical tuning steps that claw most of it back. https://blogs.damiendye.uk/en/proxmox/numa-alignment-proxmox/ Fri, 07 Aug 2026 09:40:00 +0100 https://blogs.damiendye.uk/en/proxmox/numa-alignment-proxmox/ On multi-socket systems, a VM with its vCPUs on one NUMA node and its passed-through device on another loses 20–30% throughput before you've even looked at anything else. https://blogs.damiendye.uk/en/proxmox/pcie-aspm-passthrough/ Fri, 07 Aug 2026 09:20:00 +0100 https://blogs.damiendye.uk/en/proxmox/pcie-aspm-passthrough/ Active State Power Management saves a few watts on idle PCIe links. Under VFIO passthrough, it adds latency jitter that's hard to diagnose and easy to fix. https://blogs.damiendye.uk/en/proxmox/pcie-maxpayloadsize/ Fri, 07 Aug 2026 09:00:00 +0100 https://blogs.damiendye.uk/en/proxmox/pcie-maxpayloadsize/ QEMU's virtual root complex defaults to 128-byte TLP payloads. Most devices support 256 or 512. One kernel parameter fixes it. https://blogs.damiendye.uk/en/proxmox/q35-not-i440fx/ Fri, 07 Aug 2026 08:45:00 +0100 https://blogs.damiendye.uk/en/proxmox/q35-not-i440fx/ The two QEMU virtual chipsets are not interchangeable. Q35 provides a proper PCIe topology that passthrough, modern Windows, and the wider KVM ecosystem all depend on.