Re: [PATCH 0/2] RFC: add -mem-shared option

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 29 Nov 2019 10:31:36 +0100
Paolo Bonzini <pbonzini@redhat.com> wrote:

> On 28/11/19 17:10, Eduardo Habkost wrote:
> > On Thu, Nov 28, 2019 at 06:15:16PM +0400, Marc-André Lureau wrote:  
> >> Hi,
> >>
> >> Setting up shared memory for vhost-user is a bit complicated from
> >> command line, as it requires NUMA setup such as: m 4G -object
> >> memory-backend-file,id=mem,size=4G,mem-path=/dev/shm,share=on -numa
> >> node,memdev=mem.
> >>
> >> Instead, I suggest to add a -mem-shared option for non-numa setups,
> >> that will make the -mem-path or anonymouse memory shareable.  
> > 
> > Can we make this be a "-m" option?
> > 
> > Or, even better: can we make "-m" options be automatically
> > translated to memory-backend-* options somehow?
> >   
[...]
> Therefore, I think instead of -mem-shared we should add a "-m
> memdev=..." option.  This option:
> 
> * would be mutually exclusive with both -mem-path
> 
> * would be handled from allocate_system_memory_nonnuma.
> 
> * could be mutually exclusive "-numa node", or could just be mutually
> exclusive with "-numa node,memdev=..." (the logical conclusion of that
> however would be an undeprecation of "-numa node,mem=...", so that has
> to be taken into account as well).

the plan was/still is to have memdev for main ram and deprecate
"-numa node,mem=..." for new machine types (can't be done for
old ones due to migration breakages and old libvirt which uses
it). So new machines will be forced to use "-numa memdev"
For old machines '-m memdev' provided memory region will used to
keep "-numa node,mem=..." working as it's now (however broken it is).


> 
> Paolo
> 
>