Re: 9 TiB vm memory creation

[Ani Sinha]

> > > With KVM enabled it bails out with:
> > >    qemu-system-x86_64: kvm_set_user_memory_region: 
> > > KVM_SET_USER_MEMORY_REGION failed, slot=1, start=0x100000000, 
> > > size=0x8ff40000000: Invalid argument
> > >
>
> I have seen this in my system but not always. Maybe I should have dug
> deeper as to why i do see this all the time.

Actually this would happen only wnen I was playing with memory larger than
8 TiB. So it makes sense.

I ran my script again and I can repro it right away:

2022-02-15T07:25:34.051320Z qemu-system-x86_64:
kvm_set_user_memory_region: KVM_SET_USER_MEMORY_REGION failed, slot=1,
start=0x100000000, size=0x8ff40000000: Invalid argument
kvm_set_phys_mem: error registering slot: Invalid argument

The other thing I had to do was

# echo 1 > /proc/sys/vm/overcommit_memory

otherwise the firse mmap() in mmap_activate() fails.