[Xen-devel] Regression in Xen 4.7-rc1 - can't boot HVM guests with more than 64 vCPUS.

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

The host has 240 CPUs and the HVM guests config looks as follow:

-bash-4.1# cat /hvm.cfg 
memory=64000
name="big64"
vcpus = 64
disk= ['file:/isos/root_image.iso,hdc:cdrom,r']
builder="hvm"
serial='pty'
usb=1
vnclisten="0.0.0.0:64"

-bash-4.1# xl list | grep big64 
big64                                       13 64000     1     --p---       0.0

-bash-4.1# xl dmesg | grep d13
-bash-4.1# 
-bash-4.1# head /var/log/xen/qemu-dm-big64.log 
char device redirected to /dev/pts/10 (label serial0)
qemu: hardware error: Fatal error while trying to get io event!

CPU #0:
EAX=00000000 EBX=00000000 ECX=00000000 EDX=00000663
ESI=00000000 EDI=00000000 EBP=00000000 ESP=00000000
EIP=0000fff0 EFL=00000002 [-------] CPL=0 II=0 A20=1 SMM=0 HLT=0
ES =0000 00000000 0000ffff 00009300
CS =f000 ffff0000 0000ffff 00009b00
SS =0000 00000000 0000ffff 00009300

(Attaching the full file).

If I lower the vCPUS down to 63 it boots fine.

This is todays built:
-bash-4.1# xl info
host                   : sca05-0a81fa5b
release                : 4.5.0-rc1upstream-11035-ge28f2c0
version                : #1 SMP Tue May 3 09:33:28 EDT 2016
machine                : x86_64
nr_cpus                : 240
max_cpu_id             : 239
nr_nodes               : 8
cores_per_socket       : 15
threads_per_core       : 2
cpu_mhz                : 2793
hw_caps                : 
b7ebfbff:77bee3ff:2c100800:00000001:00000001:00000281:00000000:00000100
virt_caps              : hvm hvm_directio
total_memory           : 6291334
free_memory            : 5731766
sharing_freed_memory   : 0
sharing_used_memory    : 0
outstanding_claims     : 0
free_cpus              : 0
xen_major              : 4
xen_minor              : 8
xen_extra              : Hello Again Wor
xen_version            : 4.7Hello Again Wor
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 
hvm-3.0-x86_32p hvm-3.0-x86_64 
xen_scheduler          : credit
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          : Tue May 3 12:43:35 2016 +0100 git:b90ecd5-dirty
xen_commandline        : com1=9600,8n1 dom0_mem=max:8G dom0_max_vcpus=8 
console=com1,vga loglvl=all cpufreq=verbose apic=debug
cc_compiler            : gcc (GCC) 4.4.4 20100503 (Red Hat 4.4.4-2)
cc_compile_by          : konrad
cc_compile_domain      : us.oracle.com
cc_compile_date        : Tue May  3 09:33:42 EDT 2016
build_id               : 082940fe9dc847e60892fad4c5bb1c3722022c08
xend_config_format     : 4


[konrad@vm-konrad-f22 xen]$ git log --oneline HEAD^..
b90ecd5 Final touches for Xen 4.7.0-rc1
[konrad@vm-konrad-f22 xen]$ git diff --stat
 tools/libxl/libxlu_disk_l.c | 992 
+++++++++++++++++++++++++++++++++++++++++++++++++++++-------------------------------------------
 tools/libxl/libxlu_disk_l.h |  34 +---
 2 files changed, 559 insertions(+), 467 deletions(-)

The SeaBIOS is (d14 is for the 63VCPU guest):
(d14) SeaBIOS (version rel-1.9.1-0-gb3ef39f)

Attachment: qemu-dm-big64.log
Description: Text document

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