Question

10

DMAR firmware bug. Broken BIOS?

rated 0 times [ 10] [ 0] / answers: 1 / hits: 27363 / 3 Years ago, fri, june 25, 2021, 4:22:17

I've seen below error message on my laptop screen upon loading Ubuntu just while ago but I was able to login without problem. What do you think could have gone wrong here?

DMAR: [Firmware Bug]: No firmware reserved region can cover this RMRR [0x000000008d800000-0x000000008fffffff], contact BIOS vendor for fixes

DMAR: [Firmware Bug]: Your BIOS is broken; bad RMRR [0x000000008d800000-0x000000008fffffff]

I've found more details on kernel log:

BIOS vendor: INSYDE Corp.; Ver: 5.00; Product Version: PSLZAE-00R00STE

DMAR-IR: IOAPIC id 2 under DRHD base  0xfed91000 IOMMU 1 

DMAR-IR: HPET id 0 under DRHD base 0xfed91000

DMAR-IR: x2apic is disabled because BIOS sets x2apic opt out bit.

DMAR-IR: Use 'intremap=no_x2apic_optout' to override the BIOS setting.

DMAR-IR: Enabled IRQ remapping in xapic mode

x2apic: IRQ remapping doesn't support X2APIC mode

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azaaburge

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answered 3 Years ago sweetrifiabl · Accepted Answer

DMAR firmware bug. Broken BIOS?

Yes, it is the BIOS that is giving the kernel information that is incorrect (ie. does not follow the specification).

DMAR is mainly used for GPU passthrough to a Windows virtual machine. If you do not use this you can ignore this bug otherwise you will need to look for a BIOS update.

Use 'intremap=no_x2apic_optout' to override the BIOS setting.

Use that and the bug is ignored and no longer shown. Change GRUB_CMDLINE_LINUX_DEFAULT:

sudo vi /etc/default/grub

add intremap=no_x2apic_optout nox2apic.

Add acpi=off if the system starts complaining about ACPI.

After editting do

sudo update-grub

and reboot.