Re: [PATCH v2 04/10] Introduce the CPU address space destruction function

[lixianglai]

Hi David:

> On 12.09.23 04:11, xianglai li wrote:
> > Introduce new function to destroy CPU address space resources
> > for cpu hot-(un)plug.
> How do other archs handle that? Or how are they able to get away 
> without destroying?
They do not remove the cpu address space, taking the X86 architecture as 
an example:

1.Start the x86 VM:

./qemu-system-x86_64 \
-machine q35  \
-cpu Broadwell-IBRS \
-smp 1,maxcpus=100,sockets=100,cores=1,threads=1 \
-m 4G \
-drive file=~/anolis-8.8.qcow2  \
-serial stdio   \
-monitor telnet:localhost:4498,server,nowait   \
-nographic

2.Connect the qemu monitor

telnet 127.0.0.1 4498

info mtree

address-space: cpu-memory-0
address-space: memory
  0000000000000000-ffffffffffffffff (prio 0, i/o): system
    0000000000000000-000000007fffffff (prio 0, ram): alias ram-below-4g 
@pc.ram 0000000000000000-000000007fffffff
    0000000000000000-ffffffffffffffff (prio -1, i/o): pci
      00000000000a0000-00000000000bffff (prio 1, i/o): vga-lowmem

3.Perform cpu hot swap int qemu monitor

device_add 
Broadwell-IBRS-x86_64-cpu,socket-id=1,core-id=0,thread-id=0,id=cpu1
device_del cpu1

info mtree

address-space: cpu-memory-0
address-space: cpu-memory-1
address-space: memory
  0000000000000000-ffffffffffffffff (prio 0, i/o): system
    0000000000000000-000000007fffffff (prio 0, ram): alias ram-below-4g 
@pc.ram 0000000000000000-000000007fffffff
    0000000000000000-ffffffffffffffff (prio -1, i/o): pci
      00000000000a0000-00000000000bffff (prio 1, i/o): vga-lowmem


From the above test, you can see whether the address space of cpu1 is 
residual after a cpu hot swap, and whether it is reasonable?

The address space destruction function of the CPU can be used to delete 
the residual address space of the CPU1.

Thanks,

xianglai.