[Bug 82761] DMAR:[fault reason 06] PTE Read access is not set

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https://bugzilla.kernel.org/show_bug.cgi?id=82761

--- Comment #8 from Ansa89 <ansalonistefano@gmail.com> ---
(In reply to Alex Williamson from comment #6)
> Are these 3 separate NICs plugged into PCI slots on the motherboard or is
> this a single triple-port card with embedded PCIe-to-PCI bridge?

They are 3 separate NICs plugged into 3 separate PCI slots.


> You might be able to run the IOMMU in passthrough mode with iommu=pt
> r8169.use_dac=1, but note the warning in modinfo "use_dac:Enable PCI DAC.
> Unsafe on 32 bit PCI slot."  Unfortunately if you don't enable use_dac, then
> intel_iommu will ignore the passthrough option for these devices.

I tried using "intel_iommu=pt", but it didn't work (resulted in vt-d disabled).
However with "intel_iommu=on iommu=pt" the errors remain (probably because I
didn't add "r8169.use_dac=1").
I'm on a 64 bit system, but I think it has nothing to with "32 bit PCI slot".


> Also note that this problem has nothing to do with Virtualization/KVM. 
> Drivers/Network or perhaps Drivers/PCI would be a more appropriate
> classification.

I searched for "IOMMU" section but it doesn't exist.
I will probably change classification to "Drivers/PCI".



(In reply to Alex Williamson from comment #7)
> I'm guessing this might be the motherboard here: MSI ZH77A-G43

Yes, that is my motherboard.


> Since you're apparently trying to use VT-d on this system for KVM and
> therefore presumably device assignment, I'll note that you will never be
> able to successfully assign the conventional PCI devices separately between
> guests or between host and guests.  The IOMMU does not have the granularity
> to create separate IOMMU domains per PCI slot in this topology.  Also, some
> (all?) Realtek NICs have some strange backdoors to PCI configuration space
> that make them poor targets for PCI device assignment:

Yes, I'm trying to do device assignment, but not with those NICs: I want to
pass only the nVidia PCIe VGA card to guest; while all NICs (and the integrated
VGA card) will remain available to host.
It would be nice if there would be a way to prevent IOMMU on these NICs (or
something like that).

SIDE NOTE: in the qemu commit they talk about RTL8168, but I have real RTL8169
devices (the only RTL8168 device is the integrated NIC and for that device I'm
using r8168 driver from realtek compiled by hand).

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