On 14.09.23 15:00, lixianglai wrote:
Hi David:
Hi!
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
Hm, doesn't seem to work for me on upstream QEMU for some reason:
"Error: acpi: device unplug request for not supported device type:
Broadwell-IBRS-x86_64-cpu"
What happens if you re-add that CPU? Will we reuse the previous address
space?
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?
Probably we should teach other archs to destroy that address space as well.
Can we do that from the core, instead of having to do that in each CPU
unrealize function?
--
Cheers,
David / dhildenb
