unable to boot windows with 256 cpus

[Igor Mammedov]

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.


---
*******************************************************************************
*                                                                             *
*                        Bugcheck Analysis                                    *
*                                                                             *
*******************************************************************************
 
HAL_INITIALIZATION_FAILED (5c)
Arguments:
Arg1: 0000000000007000
Arg2: 0000000000000618
Arg3: ffffffffc00000bb
Arg4: 0000000000000000
 
Debugging Details:
------------------
 
 
DEFAULT_BUCKET_ID:  WIN8_DRIVER_FAULT
 
BUGCHECK_STR:  0x5C
 
CURRENT_IRQL:  0
 
ANALYSIS_VERSION: 6.3.9600.16384 (debuggers(dbg).130821-1623) amd64fre
 
DPC_STACK_BASE:  FFFFF80225BE3FB0
 
LAST_CONTROL_TRANSFER:  from fffff80221aa9714 to fffff80221c95801
 
STACK_TEXT:  
fffff802`25bdbcd8 fffff802`21aa9714 : fffff6fc`01114af8 fffff6fb`7e0088a0 
fffff6fb`7dbf0040 fffff6fb`7dbedf80 : nt!DbgBreakPointWithStatus+0x1
fffff802`25bdbce0 fffff802`21aaabff : 00000000`00000004 00000000`00000000 
00000000`00000000 ffffffff`c00000bb : nt!KiBugCheckDebugBreak+0x14
fffff802`25bdbd50 fffff802`21c8fb94 : 00000000`0000005c 00000000`00007000 
00000000`00000618 ffffffff`c00000bb : nt!KeBugCheck2+0xdd7
fffff802`25bdc460 fffff802`2297c94a : 00000000`0000005c 00000000`00007000 
00000000`00000618 ffffffff`c00000bb : nt!KeBugCheckEx+0x104
fffff802`25bdc4a0 fffff802`2297c9ac : fffff802`20c735d0 00000000`00000000 
00000000`00000009 fffff802`20c735f0 : hal!HalpInitializeInterrupts+0x406
fffff802`25bdc4f0 fffff802`229728aa : fffff802`20c735d0 fffff802`229742ce 
fffff802`20c735d0 00000000`00000007 : hal!HalpInterruptInitDiscard+0x3c
fffff802`25bdc520 fffff802`2297221c : fffff802`00000008 00000000`00000000 
fffff802`20c735d0 00000000`00000008 : hal!HalpInterruptInitSystem+0xf6
fffff802`25bdc560 fffff802`2297c537 : fffff802`00000006 fffff802`0000000c 
fffff802`20c735d0 fffff802`20c735d0 : hal!HalpInitSystemHelper+0x44
fffff802`25bdc5c0 fffff802`2285467d : fffff802`20c735d0 fffff802`20c735d0 
fffff802`25bdc6f0 00000000`00010228 : hal!HalpInitSystemPhase0+0x1b
fffff802`25bdc5f0 fffff802`222d065f : fffff802`20c735d0 00000000`00000000 
00000000`00000000 fffff802`21cf6180 : nt!InitBootProcessor+0x265
fffff802`25bdc870 fffff802`222e4073 : fffff802`222ae400 fffff802`222aeac0 
fffff802`25bdd000 fffff802`21cf6180 : nt!KiInitializeKernel+0xd83
fffff802`25bdcc10 00000000`00000000 : 00000000`00000000 00000000`00000000 
00000000`00000000 00000000`00000000 : nt!KiSystemStartup+0x193
 
 
STACK_COMMAND:  kb
 
FOLLOWUP_IP:
nt!InitBootProcessor+265
fffff802`2285467d 84c0            test    al,al
 
SYMBOL_STACK_INDEX:  9
 
SYMBOL_NAME:  nt!InitBootProcessor+265
 
FOLLOWUP_NAME:  MachineOwner
 
MODULE_NAME: nt
 
IMAGE_NAME:  ntkrnlmp.exe
 
DEBUG_FLR_IMAGE_TIMESTAMP:  5215d150
 
IMAGE_VERSION:  6.3.9600.16384
 
BUCKET_ID_FUNC_OFFSET:  265
 
FAILURE_BUCKET_ID:  
0x5C_HAL_INTERRUPT_REMAPPING_SETUP_FAILURE_nt!InitBootProcessor
 
BUCKET_ID:  0x5C_HAL_INTERRUPT_REMAPPING_SETUP_FAILURE_nt!InitBootProcessor
 
ANALYSIS_SOURCE:  KM
 
FAILURE_ID_HASH_STRING:  
km:0x5c_hal_interrupt_remapping_setup_failure_nt!initbootprocessor
 
FAILURE_ID_HASH:  {85a33624-5d0e-3044-bbaa-0bdba50d221b}