Re: unable to boot windows with 256 cpus

[Igor Mammedov]

On Wed, 15 Jul 2020 14:28:19 -0400
Peter Xu <peterx@redhat.com> wrote:

> 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.

here is all it outputs.

480969@1594894035.927040:vtd_context_cache_reset 
480969@1594894035.928033:vtd_switch_address_space Device 00:00.0 switching 
address space (iommu enabled=0)
480969@1594894035.934110:vtd_switch_address_space Device 00:01.0 switching 
address space (iommu enabled=0)
480969@1594894035.935382:vtd_switch_address_space Device 00:02.0 switching 
address space (iommu enabled=0)
480969@1594894035.936661:vtd_switch_address_space Device 00:1f.0 switching 
address space (iommu enabled=0)
480969@1594894035.937957:vtd_switch_address_space Device 00:1f.2 switching 
address space (iommu enabled=0)
480969@1594894035.939258:vtd_switch_address_space Device 00:1f.3 switching 
address space (iommu enabled=0)
480969@1594894035.950198:vtd_context_cache_reset 
480969@1594894035.950213:vtd_switch_address_space Device 00:00.0 switching 
address space (iommu enabled=0)
480969@1594894035.950219:vtd_switch_address_space Device 00:01.0 switching 
address space (iommu enabled=0)
480969@1594894035.950224:vtd_switch_address_space Device 00:02.0 switching 
address space (iommu enabled=0)
480969@1594894035.950229:vtd_switch_address_space Device 00:1f.0 switching 
address space (iommu enabled=0)
480969@1594894035.950234:vtd_switch_address_space Device 00:1f.2 switching 
address space (iommu enabled=0)
480969@1594894035.950238:vtd_switch_address_space Device 00:1f.3 switching 
address space (iommu enabled=0)

> 
> Thanks,
>