Re: [PATCH RFC V6 05/24] arm/virt,kvm: Pre-create KVM vCPUs for 'disabled' QOM vCPUs at machine init

[Gavin Shan <gshan@redhat.com>]

Hi Salil,

On 10/23/25 11:29 AM, Salil Mehta wrote:

[...]

>>
>> Ah, I see. I think I understand the issue. It's complaining
>> about calling the  finalize twice. Is it possible to check as
>> I do not have a way to test it?
>>
>>
>> int kvm_arm_vcpu_finalize(struct kvm_vcpu *vcpu, int feature)
>> {
>> switch (feature) {
>> case KVM_ARM_VCPU_SVE:
>> [...]
>> if (kvm_arm_vcpu_sve_finalized(vcpu))
>> return -EPERM;-----> this where it must be popping?
>> [...]
>> }
> 
> I've pushed the fix to avoid calling the finalizing SVE
> feature (KVM_ARM_VCPU_FINALIZE) twice on the
> same RFC-V6.2 branch.
> 
> May I kindly request you to validate the fix again and
> check SVE works on NVIDIA grace-hopper?
> 

With the latest rfc-v6.2 branch, I don't hit the issue. The vCPU can be hot added
and removed on grace-hopper host.

host$ /home/gavin/sandbox/qemu.main/build/qemu-system-aarch64                     \
       -accel kvm -machine virt,gic-version=host,nvdimm=on                         \
       -cpu host,sve=on                                                            \
       -smp maxcpus=4,cpus=2,disabledcpus=2,sockets=2,clusters=2,cores=1,threads=1 \
       -m 4096M,slots=16,maxmem=128G                                               \
       -object memory-backend-ram,id=mem0,size=2048M                               \
       -object memory-backend-ram,id=mem1,size=2048M                               \
       -numa node,nodeid=0,memdev=mem0,cpus=0-1                                    \
       -numa node,nodeid=1,memdev=mem1,cpus=2-3                                    \
       -L /home/gavin/sandbox/qemu.main/build/pc-bios                              \
       -monitor none -serial mon:stdio -nographic -gdb tcp::6666                   \
       -qmp tcp:localhost:5555,server,wait=off                                     \
       -bios /home/gavin/sandbox/qemu.main/build/pc-bios/edk2-aarch64-code.fd      \
       -kernel /home/gavin/sandbox/linux.guest/arch/arm64/boot/Image               \
       -initrd /home/gavin/sandbox/images/rootfs.cpio.xz                           \
       -append memhp_default_state=online_movable
          :
          :
guest$ cd /sys/devices/system/cpu
guest$ cat present enabled online
0-3
0-1
0-1
(qemu) device_set host-arm-cpu,socket-id=1,cluster-id=0,core-id=0,thread-id=0,admin-state=enable
guest$ echo 1 > cpu2/online
guest$ cat present enabled online
0-3
0-2
0-2
         :
         :
guest$ cd /sys/device/system/cpu
guest$ cat present enabled online
0-3
0-2
0-2
(qemu) device_set host-arm-cpu,socket-id=1,cluster-id=0,core-id=0,thread-id=0,admin-state=disable
guest$ cat present enabled online
0-3
0-1
0-1

Thanks,
Gavin