Unix and Linux Stack Exchange
Unix and Linux Stack Exchange

Questions tagged [iommu]

35 questions
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1 answer

What are the implication of iommu=soft?

I've got new laptop at work (Lenovo A485) and there are few issues with it. It prints AMD-Vi: IOAPIC[32] not in IVRS table and kernel panic after that. So far I've figured few ways to get the system up and running. noapic - terrible performance and…
graywolf
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How can I prevent USB drivers (EHCI) from loading on specific USB controller (PCIe card)?

I'm using Debian 10.8 with Linux Kernel 4.19.0-14. I'm trying to use IOMMU to passthrough an entire USB controller (PCI Express card), but I'm having problems. The kernel is loading the ohci_pci and ehci_pci drivers and I can't seem to prevent it…
SofaKng
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What are the implication of using iommu=force in the boot kernel options?

I have to follow a hardening procedure for a linux os, in this procedure it tels us that the kernel option must have iommu=force. What does it do ? What could be the difference without specifying anything about iommu? Is it compatible with the pci…
iXô
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How does mmio get routed to io devices?

I am trying to understand how IO devices are mapped into the 'regular' memory address space on modern x86 machines running Linux. Some details which I am trying to make sense of are: cat /proc/iomem prints out a list of io memory mapped regions…
shafe
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Can a Linux Swap Partition Be Too Big?

Can a Linux swap partition be too big? I'm pretty certain the answer is, "no" but I haven't found any resources on-point, so thought I'd ask. In contrast, the main Windows swap file, pagefile.sys, can be too large. A commonly cited cap is 3x…
ebsf
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What is the appropiate iommu kernel parameter for Ryzen5 1600 and multiple RX580 GPU?

Reserving all the PCIe slot for RX580 prevents my PC to boot, due to such errors AMD-VI IOTLB_INV_TIMEOUT, AER: Corrected error received or kernel panic. Adding the linux parameters with iommu=soft and pci=noaer solves the boot issue. On Lubuntu and…
ywiyogo
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Linux, at what point a device can write to the main memory through DMA?

I am trying to figure out how and when Linux gives the permission to perform direct memory access (DMA) to the peripheral devices on PCIe. I have read how DMA is initiated in the kernel's "DMA API HOWTO", but still would like to clarify a couple…
xealits
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VT-d support enabled but IOMMU groups are missing

On a Supermicro A2SDi-8C+-HLN4F Atom C3758 system I see that VT-d support is enabled in the BIOS but I can't find any IOMMU groups under Linux (Fedora 31): $ ls /sys/kernel/iommu_groups $ The kernel logs seem to indicate that VT-d is detected: #…
maxschlepzig
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Is possible to re-add a removed iommu device?

I use pci passthrough. Unfortunately my card is sharing the same irq of an usb controller. I use this procedure: Find the sharing irq, in my case return 21 lspci -s 00:05:00 -vvv Find the irq cat /proc/interrupts|grep 21: Return me usb2 So…
elbarna
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Why does PCI passthrough not give my device to the guest OS?

I want to try PCI passthrough. I have passed an old capture video card to a Windows XP guest. IOMMU is enabled; vfio_pci is loaded I run this command: virsh nodedev-detach pci_0000_05_05_0 lspci -s 00:05 -v It reports vfio is "running" the PCI…
elbarna
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How to disable/enable bounce-buffers in IOMMU?

I am trying to figure out how to disable bounce buffers used in IOMMU when the hardware IOMMU is used. To give more context, when IOMMU_DEFAULT_DMA_STRICT is set in the kernel it enables strict IOTLB invalidations on page unmap. Also, it uses an…
sammy17
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How to fix AMD-Vi: Unable to read/write to IOMMU perf counter. at boot Void Linux

I am using an amd laptop. CPU: AMD Ryzen 5 3500U with Radeon Vega Mobile Gfx (8) @ 2.100GHz GPU: AMD ATI 03:00.0 Picasso While starting void I get this message on top AMD-Vi: Unable to read/write to IOMMU perf counter I tried some other…
Alok
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Problem with IOMMU passthrough of i915 after Debian update

Yesterday, after six stable months I upgraded my Debian 10 box to Debian 4.19.98-1+deb10u1 (2020-04-27). I am running a KVM hypervisor and Windows 10 Pro as a VM on that box. The Win VM uses the i915 graphics adapter from the Intel(R) Core(TM)…
sdittmar
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Can't access RAM from PCIe device

I use Intel Xeon with centos8 , kernel 4.18. There is also an FPGA connected to CPU through PCIe. The FPGA try to access RAM (through DMA) using physical address in RAM, but it fails in access. using older PC (Intel DUO), with same OS, FPGA, etc -…
ransh
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Difference between modprobe and pci files to remove add devices

I am trying to see how these two set of commands differ if I just have one nvme device. Block device ls -l /sys/block/nvme0n1 lrwxrwxrwx 1 root root 0 Apr 28 11:59 /sys/block/nvme0n1 ->…
pointnotfoe
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