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#1 2018-01-01 14:56:06

tfcata
Member
Registered: 2013-02-04
Posts: 25

Lots of DMAR entries in kernel log

Since I successfully turned on IOMMU with intel_iommu=on, I've noticed a lot of the following entry in the kernel log.

[  194.809429] DMAR: DRHD: handling fault status reg 3
[  194.809432] DMAR: [DMA Read] Request device [03:00.0] fault addr fffe0000 [fault reason 06] PTE Read access is not set
[  195.150607] DMAR: DRHD: handling fault status reg 3
[  195.150613] DMAR: [DMA Read] Request device [03:00.0] fault addr fffe0000 [fault reason 06] PTE Read access is not set
[  195.150770] DMAR: DRHD: handling fault status reg 3
[  195.150774] DMAR: [DMA Read] Request device [03:00.0] fault addr fffe0000 [fault reason 06] PTE Read access is not set
[  195.491960] DMAR: DRHD: handling fault status reg 3
[  195.491967] DMAR: [DMA Read] Request device [03:00.0] fault addr fffe0000 [fault reason 06] PTE Read access is not set
[  195.492115] DMAR: DRHD: handling fault status reg 3
[  195.492119] DMAR: [DMA Read] Request device [03:00.0] fault addr fffe0000 [fault reason 06] PTE Read access is not set


A quick check with lspci yields:

03:00.0 Multimedia audio controller: Creative Labs EMU10k2/CA0100/CA0102/CA10200 [Sound Blaster Audigy Series] (rev 04)

It's annoying that this happens whenever there is sound played. And the amount of the entries is huge.

So the question is how can I fix this?

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#2 2018-01-01 15:15:24

seth
Member
Registered: 2012-09-03
Posts: 51,165

Re: Lots of DMAR entries in kernel log

Successfully turn iommu off again, this btw. has lately been all over the board due to an overly optimisitic move by kernel devs.
https://bbs.archlinux.org/viewtopic.php?id=230362

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#3 2018-01-01 16:14:10

Uriel_Bernhard48
Member
Registered: 2017-08-08
Posts: 29

Re: Lots of DMAR entries in kernel log

Iommu creates issues for intel graphics. https://bugs.freedesktop.org/show_bug.cgi?id=89360

Best solution is to enable iommu but disable it for graphic device with:

intel_iommu=on,igfx_off

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#4 2018-01-01 19:13:28

loqs
Member
Registered: 2014-03-06
Posts: 17,369

Re: Lots of DMAR entries in kernel log

@Uriel_Bernhard48 but that will leave IOMMU enabled for the audio controller which is causing the DMAR faults you believe the iGPU if there is one is
somehow having an impact on the audio controller causing those errors that will be prevented by blocking the iGPU from IOMMU?
edit:
spelling causing not cuasing.

Last edited by loqs (2018-01-01 19:14:24)

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#5 2018-01-02 01:15:33

tfcata
Member
Registered: 2013-02-04
Posts: 25

Re: Lots of DMAR entries in kernel log

seth wrote:

Successfully turn iommu off again, this btw. has lately been all over the board due to an overly optimisitic move by kernel devs.
https://bbs.archlinux.org/viewtopic.php?id=230362

I turned it on because I need to passthrough the GPU. Is there any option like the one suggested above to only turn on IOMMU for the GPU?

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#6 2018-01-02 09:20:03

seth
Member
Registered: 2012-09-03
Posts: 51,165

Re: Lots of DMAR entries in kernel log

	intel_iommu=	[DMAR] Intel IOMMU driver (DMAR) option
		on
			Enable intel iommu driver.
		off
			Disable intel iommu driver.
		igfx_off [Default Off]
			By default, gfx is mapped as normal device. If a gfx
			device has a dedicated DMAR unit, the DMAR unit is
			bypassed by not enabling DMAR with this option. In
			this case, gfx device will use physical address for
			DMA.
		forcedac [x86_64]
			With this option iommu will not optimize to look
			for io virtual address below 32-bit forcing dual
			address cycle on pci bus for cards supporting greater
			than 32-bit addressing. The default is to look
			for translation below 32-bit and if not available
			then look in the higher range.
		strict [Default Off]
			With this option on every unmap_single operation will
			result in a hardware IOTLB flush operation as opposed
			to batching them for performance.
		sp_off [Default Off]
			By default, super page will be supported if Intel IOMMU
			has the capability. With this option, super page will
			not be supported.
		ecs_off [Default Off]
			By default, extended context tables will be supported if
			the hardware advertises that it has support both for the
			extended tables themselves, and also PASID support. With
			this option set, extended tables will not be used even
			on hardware which claims to support them.
		tboot_noforce [Default Off]
			Do not force the Intel IOMMU enabled under tboot.
			By default, tboot will force Intel IOMMU on, which
			could harm performance of some high-throughput
			devices like 40GBit network cards, even if identity
			mapping is enabled.
			Note that using this option lowers the security
			provided by tboot because it makes the system
			vulnerable to DMA attacks.

forcedac might work.
Did you try "iommu=soft" (NOT "intel_iommu")

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#7 2018-01-05 14:18:44

tfcata
Member
Registered: 2013-02-04
Posts: 25

Re: Lots of DMAR entries in kernel log

seth wrote:
	intel_iommu=	[DMAR] Intel IOMMU driver (DMAR) option
		on
			Enable intel iommu driver.
		off
			Disable intel iommu driver.
		igfx_off [Default Off]
			By default, gfx is mapped as normal device. If a gfx
			device has a dedicated DMAR unit, the DMAR unit is
			bypassed by not enabling DMAR with this option. In
			this case, gfx device will use physical address for
			DMA.
		forcedac [x86_64]
			With this option iommu will not optimize to look
			for io virtual address below 32-bit forcing dual
			address cycle on pci bus for cards supporting greater
			than 32-bit addressing. The default is to look
			for translation below 32-bit and if not available
			then look in the higher range.
		strict [Default Off]
			With this option on every unmap_single operation will
			result in a hardware IOTLB flush operation as opposed
			to batching them for performance.
		sp_off [Default Off]
			By default, super page will be supported if Intel IOMMU
			has the capability. With this option, super page will
			not be supported.
		ecs_off [Default Off]
			By default, extended context tables will be supported if
			the hardware advertises that it has support both for the
			extended tables themselves, and also PASID support. With
			this option set, extended tables will not be used even
			on hardware which claims to support them.
		tboot_noforce [Default Off]
			Do not force the Intel IOMMU enabled under tboot.
			By default, tboot will force Intel IOMMU on, which
			could harm performance of some high-throughput
			devices like 40GBit network cards, even if identity
			mapping is enabled.
			Note that using this option lowers the security
			provided by tboot because it makes the system
			vulnerable to DMA attacks.

forcedac might work.
Did you try "iommu=soft" (NOT "intel_iommu")

Tried both, neither worked. Perhaps it's time to report a kernel bug or something? how do I do that?

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#8 2018-01-05 14:28:36

loqs
Member
Registered: 2014-03-06
Posts: 17,369

Re: Lots of DMAR entries in kernel log

https://www.kernel.org/doc/html/latest/ … -bugs.html please do not report it on the arch bug tracker as it is an upstream issue.

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