Re: [Qemu-devel] [PATCH v3 0/2] Introduce default ram size in MachineClass

[Peter Maydell]

On 5 March 2015 at 19:24, Nikunj A Dadhania <address@hidden> wrote:
> Rejection is also change of behaviour. Because till now, a VM would
> start with any memory size, even if it's less that 128MB
> (default_ram_size). With rejection, all those VMs would fail booting
> displaying the warning. Is this OK?

No. Not all of the machines we emulate are modern machines with
gigabytes of memory -- some are very small boards which might
really only have 64K of RAM. If the user asks for 64K you should
do what they ask.

If what you want is to reject user specified memory sizes which
are too small, this is a "minimum RAM size", which is different
from "default RAM size". It would also be nice to have a
"maximum RAM size", so we can avoid weird failures if the user
asks for 1GB on a board which only has 256MB of space for RAM
in its address map.

Somebody may be along shortly to complain that this doesn't account
for machines where you can only add RAM one DRAM stick at a time
and so 64MB, 128MB and 256MB might all be valid but 100MB not.
At least, that's what happened a few years ago when I tried to
suggest something like these per-board properties...

-- PMM