Re: Error "cannot bind memory to host NUMA nodes: Operation not permitted" running inside docker

[Daniel P . Berrangé]

On Wed, Apr 29, 2020 at 11:40:32PM +0300, Manuel Hohmann wrote:
> Hi,
> 
> I encountered the following error message on the QEMU 5.0.0 release, compiled 
> and run inside a docker image:
> 
> "cannot bind memory to host NUMA nodes: Operation not permitted"

The error is reporting that mbind() failed.

mbind() man page says it gives EPERM when

  "The  flags argument included the MPOL_MF_MOVE_ALL flag and
   the caller does not have the CAP_SYS_NICE privilege."

QEMU always uses the MPOL_MF_MOVE flag though.

Looking at the kernel source,  mbind can also return EPERM if the
process is not permitted to access the requested nodes which seems
more plausible as a cause.

I guess the container the bound to some sub-set of nodes and QEMU is
trying to place the VM on different nodes that the container isn't
allowed to accesss.

> 
> The QEMU command line to reproduce this behavior (it happens also on -x86_64, 
> -arm, -aarch64 with similar command line):
> 
> qemu-system-i386 -m 64 -M pc -smp 1 -display none -monitor stdio -drive 
> file=mp-acpi/NOS.iso,media=cdrom,id=d -boot order=d -d cpu_reset

There is no reference to host mem backend or NUMA binding, so I'm
puzzled why QEMU would be doing an mbind() at all. That seems bad.


Regards,
Daniel
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