[Bug 209333] New: VM not starting anymore with 5.8.8 - lots of page faults

[Bug 209333] New: VM not starting anymore with 5.8.8 - lots of page faults

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=209333

            Bug ID: 209333
           Summary: VM not starting anymore with 5.8.8 - lots of page
                    faults
           Product: Virtualization
           Version: unspecified
    Kernel Version: 5.8.8
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: kvm
          Assignee: virtualization_kvm@kernel-bugs.osdl.org
          Reporter: kernel@martin.schrodt.org
        Regression: No

Host system is a Threadripper 1920x on a X399 Motherboard.
I have a VM here, that I pass through a Samsung 960 EVO SSD. 

> 08:00.0 Non-Volatile memory controller: Samsung Electronics Co Ltd NVMe SSD
> Controller SM961/PM961

The VM starts up and works fine with Kernel 5.8.7, and when I start the VM with
a 5.8.8 kernel, libvirt/QEMU say the VM is started, but it doesn't come up, and
I see lots and lots of these in dmesg:

> AMD-Vi: Event logged [IO_PAGE_FAULT device=08:00.0 domain=0x002c
> address=0xfffffffdf8000000 flags=0x0008]

Now, one thing to mention is that the VM uses AMD AVIC to directly deliver
interrupts to the VM.

There are 2 IOMMU related changes in the 5.8.8 changelog that seem likely for
the layman that I am, both by Suravee Suthikulpanit from AMD:

iommu/amd: Use cmpxchg_double() when updating 128-bit IRTE
iommu/amd: Restore IRTE.RemapEn bit after programming IRTE

I observe the same behaviour with 5.8.10.

Happy to provide more info if needed!

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[Bug 209333] VM not starting anymore with 5.8.8 - lots of page faults

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=209333

Martin Schrodt (kernel@martin.schrodt.org) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|kvm                         |IOMMU
            Version|unspecified                 |2.5
            Product|Virtualization              |Drivers

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[Bug 209333] VM not starting anymore with 5.8.8 - lots of page faults

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=209333

Martin Schrodt (kernel@martin.schrodt.org) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Hardware|All                         |Intel

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[Bug 209333] VM not starting anymore with 5.8.8 - lots of page faults

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=209333

Maxim Levitsky (maximlevitsky@gmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |maximlevitsky@gmail.com

--- Comment #1 from Maxim Levitsky (maximlevitsky@gmail.com) ---
I bisected and reported this regression few days ago. The fix is upstream and
probably will land to the stable trees as well.

https://lkml.org/lkml/2020/9/13/94

https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg2312235.html

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[Bug 209333] VM not starting anymore with 5.8.8 - lots of page faults

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=209333

--- Comment #2 from Martin Schrodt (kernel@martin.schrodt.org) ---
Jep.

The change made it into 5.8.11.

Thanks for the quick fix too all involved!

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