[Bug 215459] VM freezes starting with kernel 5.15

[bugzilla-daemon@bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=215459

--- Comment #2 from th3voic3@mailbox.org ---
(In reply to mlevitsk from comment #1)
> On Thu, 2022-01-06 at 11:03 +0000, bugzilla-daemon@bugzilla.kernel.org wrote:
> > https://bugzilla.kernel.org/show_bug.cgi?id=215459
> > 
> >             Bug ID: 215459
> >            Summary: VM freezes starting with kernel 5.15
> >            Product: Virtualization
> >            Version: unspecified
> >     Kernel Version: 5.15.*
> >           Hardware: Intel
> >                 OS: Linux
> >               Tree: Mainline
> >             Status: NEW
> >           Severity: normal
> >           Priority: P1
> >          Component: kvm
> >           Assignee: virtualization_kvm@kernel-bugs.osdl.org
> >           Reporter: th3voic3@mailbox.org
> >         Regression: No
> > 
> > Created attachment 300234 [details]
> >   --> https://bugzilla.kernel.org/attachment.cgi?id=300234&action=edit
> > qemu.hook and libvirt xml
> > 
> > Hi,
> > 
> > starting with kernel 5.15 I'm experiencing freezes in my VFIO Windows 10
> VM.
> > Downgrading to 5.14.16 fixes the issue.
> > 
> > I can't find any error messages in dmesg when this happens and comparing
> the
> > dmesg output between 5.14.16 and 5.15.7 didn't show any differences.
> > 
> > 
> > Additional info:
> > * 5.15.x
> > * I'm attaching my libvirt config and my /etc/libvirt/hooks/qemu
> > * My specs are:
> > ** i7-10700k
> > ** ASUS z490-A PRIME Motherboard
> > ** 64 GB RAM
> > ** Passthrough Card: NVIDIA 2070 Super
> > ** Host is using the integrated Graphics chip
> > 
> > Steps to reproduce:
> > Boot any 5.15 kernel and start the VM and after some time (no specific
> > trigger
> > as far as I can see) the VM freezes.
> > 
> > After some testing the solution seems to be:
> > 
> > I read about this:
> > 20210713142023.106183-9-mlevitsk@redhat.com/#24319635">
> >
> >
> https://patchwork.kernel.org/project/kvm/patch/20210713142023.106183-9-mlevitsk@redhat.com/#24319635
> > 
> > And so I checked
> > cat /sys/module/kvm_intel/parameters/enable_apicv
> > 
> > which returns Y to me by default.
> > 
> > So I added
> > options kvm_intel enable_apicv=0
> > to /etc/modprobe.d/kvm.conf
> > 
> > 
> > cat /sys/module/kvm_intel/parameters/enable_apicv
> > now returns N
> > 
> > So far I haven't encountered any freezes.
> > 
> > The confusing part is that APICv shouldn't be available with my CPU
> 
> I guess you are lucky and your cpu has it? 
> Does /sys/module/kvm_intel/parameters/enable_apicv show Y on 5.14.16 as well?
Yep just checked again.

> 
> I know that there were few fixes in regard to posted interrupts on intel,
> which might explain the problem.
I tried checking with
for i in $(find /sys/class/iommu/dmar* -type l); do echo -n "$i: "; echo $(( (
0x$(cat $i/intel-iommu/cap) >> 59 ) & 1 )); done
cat: /intel-iommu/cap: No such file or directory
/sys/class/iommu/dmar0: 0
/sys/class/iommu/dmar1: 0


So posted interrupts don't work on my system anyways?


> 
> You might want to try 5.16 kernel when it released.
I will definitely check again thanks.

Assuming I really do have APICv: is there anything I need to change in my XML
to really make use of this feature or does it work "out of the box"?

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