Re: Core dump happened when starting a VM on arm64 server

[Philippe Mathieu-Daudé]

On 6/11/20 11:14 AM, Andrew Jones wrote:
> On Thu, Jun 11, 2020 at 04:46:45PM +0800, Haibo Xu wrote:
>> Hi,
>>
>> I met a qemu core dump issue when starting a VM with cpu feature
>> "pmu=on" on an arm server.
>> The commands to start the machine is:
>>
>>   ./qemu-system-aarch64 \
>>            -cpu host,pmu=on -M virt,accel=kvm,gic-version=3 -nographic
>> -m 2048M \
>>            -kernel ./Image \
>>            -initrd /boot/initrd.img-5.6.0-rc2+ \
>>            -append "root=/dev/vda rw console=ttyAMA0" -nodefaults -serial 
>> stdio\
>>            -drive if=none,file=./xenial.rootfs.ext4,id=hd0,format=raw \
>>            -device virtio-blk-device,drive=hd0
>>
>>
>> And here is the stack dump:
>>
>>  Core was generated by `./qemu-system-aarch64 -cpu host,pmu=on -M
>> virt,accel=kvm,gic-version=3 -nograph'.
>>  Program terminated with signal SIGSEGV, Segmentation fault.
>>  #0  kvm_ioctl (s=0x0, type=type@entry=44547) at
> 
> s=0x0 means cpu->kvm_state is NULL
> 
>> The root cause is in the arm_get_pmu() operation which was introduced
>> in ae502508f83.
> 
> Actually the root cause is d70c996df23f ("target/arm/kvm: Use
> CPUState::kvm_state in kvm_arm_pmu_supported()"). ae502508f83 used
> the machine kvm_state, not the cpu kvm_state, and that allows pmu=on
> to work. d70c996df23f changed that saying that "KVMState is already
> accessible via CPUState::kvm_state, use it.", but I'm not sure why,
> since kvm_init_vcpu() doesn't run until the vcpu thread is created.
> 
> Philippe?

Sorry for some reason I missed this email. I'll look at this today.

> 
> Thanks,
> drew
>