Changes from v1: - added more context in the commit message - added David's R-b v1 link: https://lists.gnu.org/archive/html/qemu-devel/2021-04/msg03145.html
Hi, This is the QEMU side of a kernel change being proposed in [1], where an attempt to implement a CPU hotunplug error report mechanism was proposed. The idea was discussed first in this mailing list [2], where the RTAS set-indicator call would be used to signal QEMU when a kernel side error happens during the unplug process. Using the modified kernel and this patch, this is the result of a failed CPU hotunplug attempt when trying to unplug the last online CPU of the guest: ( QEMU command line: qemu-system-ppc64 -machine pseries,accel=kvm,usb=off -smp 1,maxcpus=2,threads=1,cores=2,sockets=1 ... ) [root@localhost ~]# QEMU 5.2.92 monitor - type 'help' for more information (qemu) device_add host-spapr-cpu-core,core-id=1,id=core1 (qemu) [root@localhost ~]# echo 0 > /sys/devices/system/cpu/cpu0/online [ 77.548442][ T13] IRQ 19: no longer affine to CPU0 [ 77.548452][ T13] IRQ 20: no longer affine to CPU0 [ 77.548458][ T13] IRQ 256: no longer affine to CPU0 [ 77.548465][ T13] IRQ 258: no longer affine to CPU0 [ 77.548472][ T13] IRQ 259: no longer affine to CPU0 [ 77.548479][ T13] IRQ 260: no longer affine to CPU0 [ 77.548485][ T13] IRQ 261: no longer affine to CPU0 [ 77.548590][ T0] cpu 0 (hwid 0) Ready to die... [root@localhost ~]# (qemu) (qemu) device_del core1 (qemu) [ 83.214073][ T100] pseries-hotplug-cpu: Failed to offline CPU PowerPC,POWER9, rc: -16 qemu-system-ppc64: Device hotunplug rejected by the guest for device core1 (qemu) As mentioned in the kernel change, if this is accepted I'll push for a PAPR change to make this an official device removal error report mechanism. [1] https://lore.kernel.org/linuxppc-dev/20210416210216.380291-3-danielhb...@gmail.com/ [2] https://lists.gnu.org/archive/html/qemu-devel/2021-02/msg06395.html Daniel Henrique Barboza (1): spapr_drc.c: handle hotunplug errors in drc_unisolate_logical() hw/ppc/spapr_drc.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) -- 2.30.2
