Header7F engineering guideshttps://header7f.com/blog/Linux PCIe investigation and reproducible engineering evidence.enIOMMU groups explained: check, read and fix them for VFIO passthroughhttps://header7f.com/blog/iommu-groups-explained/https://header7f.com/blog/iommu-groups-explained/Mon, 19 Oct 2026 00:00:00 GMTWhat an IOMMU group is, how to list IOMMU groups on Linux, how to read a shared group, and safer fixes for VFIO passthrough than the ACS override.GPU passthrough on Proxmox with VFIO: the troubleshooting guidehttps://header7f.com/blog/proxmox-gpu-passthrough-troubleshooting/https://header7f.com/blog/proxmox-gpu-passthrough-troubleshooting/Mon, 19 Oct 2026 00:00:00 GMTTroubleshoot Proxmox GPU passthrough with VFIO, stage by stage: IOMMU, IOMMU groups, vfio-pci binding, q35/OVMF settings, “group is not viable” and resets.lspci explained: read lspci -vvv field by fieldhttps://header7f.com/blog/lspci-vvv-explained/https://header7f.com/blog/lspci-vvv-explained/Mon, 19 Oct 2026 00:00:00 GMTRead lspci -vvv output field by field: device line, Control/Status, BAR regions, capabilities, LnkCap vs LnkSta and “downgraded”, AER bits, drivers and setpci.PCIe errors on Linux: AER corrected vs uncorrectable, explainedhttps://header7f.com/blog/pcie-errors-aer-linux/https://header7f.com/blog/pcie-errors-aer-linux/Mon, 19 Oct 2026 00:00:00 GMTPCIe Bus Error severity=Corrected in dmesg? What AER corrected, non-fatal and fatal errors mean on Linux, when to worry and how to track them.PCIe ASPM on Linux: when pcie_aspm=off fixes errors — and what it hideshttps://header7f.com/blog/pcie-aspm-linux/https://header7f.com/blog/pcie-aspm-linux/Mon, 19 Oct 2026 00:00:00 GMTpcie_aspm=off makes Linux leave ASPM alone; it doesn’t force it off. Check real link power states with lspci and sysfs, and see what the fix hides.PCIe BARs explained: BAR0–5, sizing, MMIO, Above 4G decoding and “can’t assign; no space”https://header7f.com/blog/pcie-bar-explained/https://header7f.com/blog/pcie-bar-explained/Mon, 19 Oct 2026 00:00:00 GMTWhat a PCIe BAR is, how BAR0–5 sizing and MMIO work, why Above 4G decoding and Resizable BAR matter, and how to fix Linux “can’t assign; no space”.XDMA vs QDMA: which AMD PCIe DMA IP — and how to run the XDMA driver on Linuxhttps://header7f.com/blog/xdma-vs-qdma-linux-driver/https://header7f.com/blog/xdma-vs-qdma-linux-driver/Mon, 19 Oct 2026 00:00:00 GMTXDMA (PG195) vs QDMA (PG302): channels vs queues, H2C/C2H, the BAR layout, and how to build, load and test the Xilinx XDMA driver on Linux without timeouts.PCIe link training, speed and width: why your link is x8, x1 or “downgraded”https://header7f.com/blog/pcie-link-training-speed-width/https://header7f.com/blog/pcie-link-training-speed-width/Mon, 19 Oct 2026 00:00:00 GMTWhy lspci says LnkSta downgraded or your GPU runs at x8 instead of x16: how PCIe link training sets speed and width, LTSSM states, bifurcation and Linux triage.“GPU has fallen off the bus” / Xid 79 on Linux: an AER-first triagehttps://header7f.com/blog/gpu-fallen-off-the-bus-xid-79/https://header7f.com/blog/gpu-fallen-off-the-bus-xid-79/Mon, 19 Oct 2026 00:00:00 GMTNVIDIA Xid 79, “GPU has fallen off the bus”, means the GPU stopped answering on PCIe. Find the cause in AER, DPC, D3cold and power evidence before swapping parts.Mining rig PCIe risers: why x1 is enough — and why your rig still crasheshttps://header7f.com/blog/mining-rig-pcie-riser-x1-crashes/https://header7f.com/blog/mining-rig-pcie-riser-x1-crashes/Mon, 19 Oct 2026 00:00:00 GMTWhy a PCIe x1 riser is enough for GPU mining, and how to trace HiveOS or Linux rig crashes to AER physical-layer errors, riser cables and power.Buying a used mining GPU for AI or gaming? Read its PCIe link and error history firsthttps://header7f.com/blog/used-mining-gpu-pcie-link-check/https://header7f.com/blog/used-mining-gpu-pcie-link-check/Mon, 19 Oct 2026 00:00:00 GMTCheck a used mining GPU before you buy: compare PCIe LnkCap with LnkSta, read AER and replay counters, then stress-test VRAM, temperatures and fans.DMA attacks: how a PCIe or Thunderbolt device could read your crypto wallet’s keys — and how IOMMU stops ithttps://header7f.com/blog/dma-attack-crypto-wallet-iommu/https://header7f.com/blog/dma-attack-crypto-wallet-iommu/Mon, 19 Oct 2026 00:00:00 GMTHow a DMA attack over PCIe or Thunderbolt could expose hot-wallet keys in RAM, and how IOMMU, Kernel DMA Protection and hardware wallets defend you.FPGA not detected in lspci: Linux PCIe enumeration guidehttps://header7f.com/blog/fpga-not-in-lspci/https://header7f.com/blog/fpga-not-in-lspci/Mon, 19 Oct 2026 00:00:00 GMTInvestigate an FPGA PCIe card missing from Linux lspci. Capture the PCI tree and upstream context, distinguish reset and configuration timing, and preserve a reproducible baseline.XDMA PCIe link stuck at x1: compare Linux link evidencehttps://header7f.com/blog/xdma-link-x1/https://header7f.com/blog/xdma-link-x1/Mon, 19 Oct 2026 00:00:00 GMTInvestigate an XDMA FPGA link at x1 or a lower speed on Linux. Compare endpoint and upstream capabilities, slot wiring, controlled-load captures, AER deltas and FPGA debug evidence.Unknown header type 7f: meaning, causes and safe fixeshttps://header7f.com/blog/unknown-header-type-7f/https://header7f.com/blog/unknown-header-type-7f/Sun, 18 Oct 2026 00:00:00 GMTUnderstand lspci unknown header type 7f, rev ff and header type 127. Identify the failing PCIe device and choose a GPU, VFIO, network or FPGA recovery path.NVIDIA GPU unknown header type 7f on Ubuntu: diagnosis and fixeshttps://header7f.com/blog/nvidia-gpu-unknown-header-type-7f/https://header7f.com/blog/nvidia-gpu-unknown-header-type-7f/Sun, 18 Oct 2026 00:00:00 GMTTroubleshoot an NVIDIA GPU showing unknown header type 7f on Ubuntu or Linux. Separate PCIe access loss, Xid 79, suspend failures and signed-driver issues.Unknown PCI header type 127: Proxmox and VFIO GPU troubleshootinghttps://header7f.com/blog/proxmox-vfio-unknown-pci-header-type-127/https://header7f.com/blog/proxmox-vfio-unknown-pci-header-type-127/Sun, 18 Oct 2026 00:00:00 GMTDiagnose unknown PCI header type 127 or 7f during GPU passthrough. Compare host state before VM start, after shutdown and after restart without blind reset scripts.Thunderbolt eGPU unknown header type 7f: Linux dock troubleshootinghttps://header7f.com/blog/thunderbolt-egpu-unknown-header-type-7f/https://header7f.com/blog/thunderbolt-egpu-unknown-header-type-7f/Sun, 18 Oct 2026 00:00:00 GMTTroubleshoot unknown header type 7f on a Linux Thunderbolt eGPU or PCIe dock. Check authorization, PCIe tunneling, cables and hotplug versus suspend behavior.Wi-Fi or Ethernet unknown header type 7f: Linux recovery checkshttps://header7f.com/blog/wifi-ethernet-unknown-header-type-7f/https://header7f.com/blog/wifi-ethernet-unknown-header-type-7f/Sun, 18 Oct 2026 00:00:00 GMTDiagnose unknown header type 7f on PCIe Wi-Fi and Ethernet adapters. Check device visibility, dual-boot Fast Startup, suspend failures and driver evidence.FPGA PCIe unknown header type 7f after programming: bring-up guidehttps://header7f.com/blog/fpga-pcie-unknown-header-type-7f/https://header7f.com/blog/fpga-pcie-unknown-header-type-7f/Sun, 18 Oct 2026 00:00:00 GMTDiagnose unknown header type 7f after reprogramming an FPGA PCIe endpoint. Check enumeration timing, warm restart behavior, reference designs and host state.esd CAN/402 unknown header type 7f: kernel fix and ASPM workaroundhttps://header7f.com/blog/esd-can402-unknown-header-type-7f/https://header7f.com/blog/esd-can402-unknown-header-type-7f/Sun, 18 Oct 2026 00:00:00 GMTCheck whether esd’s CAN/402 bridge erratum applies to your card and whether your kernel contains the fix. Use the documented ASPM workaround only when appropriate.