Re: [REGRESSION][BISECTED] from bd9bbc96e835: cannot boot Win11 KVM guest

From: Ranguvar
Date: Mon Dec 16 2024 - 15:41:08 EST


On Monday, December 16th, 2024 at 16:50, Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> On Mon, Dec 16, 2024, Juri Lelli wrote:
>
> > On 14/12/24 19:52, Peter Zijlstra wrote:
> >
> > > On Sat, Dec 14, 2024 at 06:32:57AM +0000, Ranguvar wrote:
> > >
> > > > I have in kernel cmdline `iommu=pt isolcpus=1-7,17-23 rcu_nocbs=1-7,17-23 nohz_full=1-7,17-23`. Removing iommu=pt does not produce a change, and
> > > > dropping the core isolation freezes the host on VM startup.
>
> As in, dropping all of isolcpus, rcu_nocbs, and nohz_full? Or just dropping
> isolcpus?

Thanks for looking.
I had dropped all three, but not altered the VM guest config, which is:

<cputune>
<vcpupin vcpu='0' cpuset='2'/>
<vcpupin vcpu='1' cpuset='18'/>
...
<vcpupin vcpu='11' cpuset='23'/>
<emulatorpin cpuset='1,17'/>
<iothreadpin iothread='1' cpuset='1,17'/>
<vcpusched vcpus='0' scheduler='fifo' priority='95'/>
...
<iothreadsched iothreads='1' scheduler='fifo' priority='50'/>
</cputune>

CPU mode is host-passthrough, cache mode is passthrough.

The 24GB VRAM did cause trouble when setting up resizeable BAR months ago as well. It necessitated a special qemu config:
<qemu:commandline>
<qemu:arg value='-fw_cfg'/>
<qemu:arg value='opt/ovmf/PciMmio64Mb,string=65536'/>
</qemu:commandline>