Hi,All:
 
I have a CentOS 7 laptop with kernel 4.8 and Xen 4.8, the configure in /etc/grub2.cfg is:
 
menuentry 'CentOS Linux, with Xen hypervisor' --class gnu-linux --class gnu --class os --class xen $menuentry_id_option 'xen-gnulinux-simple-ba1c3f9f-2f33-a74d-b82c-75c4d7b5238a' {
        insmod part_msdos
        insmod ext2
        set root='hd0,msdos1'
        if [ x$feature_platform_search_hint = xy ]; then
          search --no-floppy --fs-uuid --set=root --hint='hd0,msdos1'  ba1c3f9f-2f33-a74d-b82c-75c4d7b5238a
        else
          search --no-floppy --fs-uuid --set=root ba1c3f9f-2f33-a74d-b82c-75c4d7b5238a
        fi
        echo    'Loading Xen 4.8.0 ...'
        if [ "$grub_platform" = "pc" -o "$grub_platform" = "" ]; then
            xen_rm_opts=
        else
            xen_rm_opts="no-real-mode edd=off"
        fi
        multiboot       /boot/xen-4.8.0.gz placeholder   ${xen_rm_opts}
        echo    'Loading Linux 4.8.0 ...'
        module  /boot/vmlinuz-4.8.0 placeholder root=UUID=ba1c3f9f-2f33-a74d-b82c-75c4d7b5238a ro crashkernel=512M@64M rhgb quiet ipv6.disable=1 
        echo    'Loading initial ramdisk ...'
        module  --nounzip   /boot/initramfs-4.8.0.img
}
 
The kdump service doesn’t work after reboot, I tried to execute “bash -x /usr/bin/kdumpctl restart”, it showed
 
+ /sbin/kexec -p '--command-line=placeholder ro rhgb quiet ipv6.disable=1 irqpoll nr_cpus=1 reset_devices cgroup_disable=memory mce=off numa=off udev.children-max=2 panic=10 rootflags=nofail acpi_no_memhotplug transparent_hugepage=never nokaslr novmcoredd disable_cpu_apicid=0' --initrd=/boot/initramfs-4.8.0kdump.img /boot/vmlinuz-4.8.0
Memory for crashkernel is not reserved
Please reserve memory by passing "crashkernel=X@Y" parameter to kernel
Then try to loading kdump kernel
+ '[' 1 == 0 ']'
+ echo 'kexec: failed to load kdump kernel'
kexec: failed to load kdump kernel
 
so How to start Dom0's kdump on CentOS 7?
 
Thanks !