[libvirt] Error when creating VM with persistent memory

[Michal Prívozník]

On 9/4/19 6:31 PM, Dan Williams wrote:
> On Wed, Sep 4, 2019 at 12:56 AM Seema Pandit <pan.blr.17 at gmail.com> wrote:
>>
>> Actually there is still some issue around this. When trying to start another VM, so using even more pmem, there is a different issue now. Error copied below.
>>
>> []# virsh start manual_clone
>>
>> error: Failed to start domain manual_clone
>>
>> error: internal error: qemu unexpectedly closed the monitor: ftruncate: Invalid argument
>>
>> 2019-09-03T21:28:41.031924Z qemu-system-x86_64: -object memory-backend-file,id=memnvdimm0,prealloc=yes,mem-path=/dev/dax1.1,share=yes,size=73014444032: os_mem_prealloc: Insufficient free host memory pages available to allocate guest RAM
> 
> /dev/dax instances do not support the ftruncate syscall, and
> device-dax instances are already fully allocated by definition. The
> prealloc option is simply invalid for /dev/dax targets.

Ah, in that case we need an XML knob that if set doesn't put
prealloc=yes onto the qemu cmd line. Unfortunatelly, I don't think I
have any spare time to implement that, so please be my guest.

Michal