Re: unable to boot windows with 256 cpus

[Peter Xu]

On Wed, Jul 15, 2020 at 07:45:13PM +0200, Igor Mammedov wrote:
> While testing ACPI cpu hotplug changes I stumbled on BSOD in case
> QEMU is configured with 256 CPUs, Windows Server 2012R2x64 fails to boot
> with bugcheck 5C
> 
> 
> qemu-system-x86_64 -m 4G -smp 2,sockets=64,cores=4,maxcpus=256 -M 
> q35,kernel-irqchip=split  -enable-kvm -device intel-iommu,intremap=on,eim=on 
> ws2012r2x64DCchk.qcow2
> 
> Looking at stacktrace, it seems that is fails when trying to initialize iommu
> 
> hal_interrupt_remapping_setup_failure_nt!initbootprocessor
> 
> Any idea what to try to figure out what QEMU is missing wrt intremap?
> 
> PS:
> WS2016 boots eventually, but CPU hotplug doesn't work, symptoms (unconfirmed 
> yet) like SCI isn't being delivered.
> With RHEL76 the same config works fine.

Igor,

Could you try this again but with vtd tracepoints enabled?

  -trace enable="vtd_*"

I think we don't need to capture all the trace outputs, but only until when the
HAL error message triggered should work.

Thanks,

-- 
Peter Xu