Re: [Qemu-devel] [RFC v2 3/6] memory: support unmapping of MemoryRegion mapped into HVA parent

[Paolo Bonzini]

On 17/06/2015 17:10, Michael S. Tsirkin wrote:
> > Actually memory_region_add_subregion(cannot fail) will continue to casue 
> > problems
> > in case one of the listeners fails and has no way to propagate error up the 
> > stack.
> > It could be that vhost_set_memory() or kvm_set_memslots() aren't able to 
> > allocate
> > memory for replacement table in low memory conditions and without
> > way to report back QEMU is left with option to die.
> 
> mmap reserving memory just adds it to a data structure somewhere
> within glibc, doesn't it? Looks like it's highly unlikely to fail,
> so maybe killing QEMU if it does isn't a big deal.

It's in the kernel, but yes, a MAP_NORESERVE mmap is highly unlikely to
fail.

Paolo