qemu backend tries to allocate millions of megabytes of memory

[Saviq]

Between #654 and #650 the qemu backend started allocating petabytes of memory... Failing, obviously.

[ricab]

From man qemu-system-x86_64

   -m [size=]megs[,slots=n,maxmem=size]
       Sets guest startup RAM size to megs megabytes. Default is 128 MiB.  Optionally, a
       suffix of "M" or "G" can be used to signify a value in megabytes or gigabytes
       respectively.

So qemu's memory resolution is megabytes. We will floor when an exact match is not possible.

[ricab]

Also interesting: https://libvirt.org/formatdomain.html#elementsMemoryAllocation

In particular

[...] the value will be rounded up to the nearest kibibyte by libvirt, and may be further rounded to the granularity supported by the hypervisor. Some hypervisors also enforce a minimum, such as 4000KiB. [...]"