[Bug 81841] amd-iommu: kernel BUG & lockup after shutting down KVM guest using PCI passthrough/PCIe bridge

[bugzilla-daemon@bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=81841

--- Comment #16 from Alex Williamson <alex.williamson@redhat.com> ---
(In reply to Joel Schopp from comment #15)
> > (In reply to Joel Schopp from comment #10)
> > > > AMD would need to confirm it.
> > >
> > > I don't have an answer for you offhand.  Let me do some digging and get you
> > > an answer.
> > 
> > I am sorry if I sounded frustrated or arrogant earlier. Any update on this?
> 
> It's not clear to me which devices were being put in the same group.  Here's
> some of my notes on your lspci output

Marti, the output of 'find /sys/kernel/iommu_groups' would be useful here. 
I'll try to help based on what I think is happening...

> lspci -vt
> -[0000:00]-+-00.0  Advanced Micro Devices, Inc. [AMD] Device 1422
>            +-00.2  Advanced Micro Devices, Inc. [AMD] Device 1423
>            +-01.0  Advanced Micro Devices, Inc. [AMD/ATI] Kaveri [Radeon R7
> 200 Series]
>            +-01.1  Advanced Micro Devices, Inc. [AMD/ATI] Device 1308
>            +-02.0  Advanced Micro Devices, Inc. [AMD] Device 1424
>            +-03.0  Advanced Micro Devices, Inc. [AMD] Device 1424
>            +-04.0  Advanced Micro Devices, Inc. [AMD] Device 1424
>            +-10.0  Advanced Micro Devices, Inc. [AMD] FCH USB XHCI Controller
>            +-10.1  Advanced Micro Devices, Inc. [AMD] FCH USB XHCI Controller
> 
> These xhci controllers are isolated from from the other devices, I would
> need some more detail on which variant you are running to determine if they
> are isolated from eachother, they probably aren't.

10.0 & 10.1 will typically be grouped together due to lack of ACS.  This is
usually not a problem.

>            +-11.0  Advanced Micro Devices, Inc. [AMD] FCH SATA Controller
> [AHCI mode]
> The sata controller is isolated from the other devices

Yep, and it's a single function device so IOMMU groups should be ok.

>            +-12.0  Advanced Micro Devices, Inc. [AMD] FCH USB OHCI Controller
>            +-12.2  Advanced Micro Devices, Inc. [AMD] FCH USB EHCI Controller
> This pair of OHCI/EHCI controllers are together isolated from the other
> devices

Yep, same as above.

>            +-13.0  Advanced Micro Devices, Inc. [AMD] FCH USB OHCI Controller
>            +-13.2  Advanced Micro Devices, Inc. [AMD] FCH USB EHCI Controller
> This pair of OHCI/EHCI controllers are together isolated from the other
> devices

Yep

>            +-14.0  Advanced Micro Devices, Inc. [AMD] FCH SMBus Controller
>            +-14.1  Advanced Micro Devices, Inc. [AMD] FCH IDE Controller
>            +-14.2  Advanced Micro Devices, Inc. [AMD] FCH Azalia Controller
>            +-14.3  Advanced Micro Devices, Inc. [AMD] FCH LPC Bridge
> I do not think the SMBus/IDE/Azalia/LPC are isolated from eachother, but
> they are isolated from the other devices I have identified.
> 
> 
>            +-14.4-[01]----05.0  Dialogic Corporation PRI
> The legacy PCI should be isolated from the other devices identified.  Not
> sure what is going on here.
> 
>            +-14.5  Advanced Micro Devices, Inc. [AMD] FCH USB OHCI Controller
> This OHCI Controller should also be isolated from the other devices.

All of the above will be grouped together, this is the problem.  Since none of
these functions support ACS, IOMMU groups assume that peer-to-peer between
functions is possible.  If 14.4 and 14.5 are truly isolated from the rest of
the package then we should have quirks to support that.  This whole block is an
update or the quirk already shown in comment 7.

>            +-15.0-[02]--
>            +-15.2-[03]----00.0  ASMedia Technology Inc. ASM1042 SuperSpeed
> USB Host Controller
> Is this in a PCI-e slot or otherwise attached to the PCI-e?
> 
>            +-15.3-[04]----00.0  Qualcomm Atheros QCA8171 Gigabit Ethernet
> Is this in a PCI-e slot or otherwise attached to the PCI-e?

I would guess 15.x are all PCIe root ports, hopefully with ACS support.

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