VT-D Keeps Disabling Itself on Dell XPS 15 9530

User Support Hardware Issues
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Device Info:
Name: DELL XPS 15 9530
GPU: GeForce RTX 4070
CPU: I9-13900H

The VT-D Setting keeps disabling itself which is preventing me from using Qubes does anyone know to fix this?

Tried the Following:
Hyper-V is Enabled
BIOS is on Latest Version

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Does it disable itself if you enable it, leave the bios, power down and power up and check it in the bios?

Are you sure you save the changes when exiting the bios?

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Yes, I Hit Apply Changes then Exit

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did you reply yes to this question or the other?

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Yes

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I have a Dell XPS 15 9520, that until today had VT-D set in BIOS, and has been running Qubes with few issues. Today the setting will not stay in place. Launching an HVM gives the error: “Failed to start an HVM qube with PCI devices assigned - hardware does not support IOMMU/VT-D/AMD-Vi.” (Upgrading BIOS does not help, resetting BIOS to defaults does not help.)

In checking, no change in BIOS seems to stay changed any longer. Perhaps you could check the following: Will any BIOS change stay changed?

Since my PC is still under warranty, it’s going back to Dell for repair.

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Do you see any flashing sequence of the status LED when you turn the laptop on? Does the time and date get reset, also?
It would be unusual for a pc under warranty, but a dead CMOS battery could cause this problem. I think there will be an led sequence for this…

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PC boots, I can run Qubes, can log into dom0. The issue is the BIOS no longer will keep a setting for VT-D, so HVM’s cannot start when then have PCI devices defined on the Devices Tab. I’ll check the battery, but I doubt that’s an issue because time is ok. I think it’s the motherboard perhaps, or something affecting BIOS.

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Yes, I think all my motherboards have lost the RTC when they forgot the BIOS settings because of the coin cell. If there is also no LED diagnostic then I guess it is probably not that.
[Edit: I found a service manual for Dell XPS which seems to say that 25 seconds holding the power button while plugged in will clear most BIOS settings… seems like a nasty feature if you have an untidy desk]

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Dell replaced the motherboard, laptop is working again.

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