Re: [Qemu-devel] [RFC] exec: eliminate ram naming issue as migration

[Tan, Jianfeng]

> -----Original Message-----
> From: Igor Mammedov [mailto:address@hidden
> Sent: Monday, February 26, 2018 8:56 PM
> To: Tan, Jianfeng
> Cc: Paolo Bonzini; Jason Wang; Maxime Coquelin; address@hidden;
> Michael S . Tsirkin
> Subject: Re: [Qemu-devel] [RFC] exec: eliminate ram naming issue as
> migration
> 
> On Sat, 24 Feb 2018 03:11:30 +0000
> "Tan, Jianfeng" <address@hidden> wrote:
> 
> > > -----Original Message-----
> > > From: Tan, Jianfeng
> > > Sent: Saturday, February 24, 2018 11:08 AM
> > > To: 'Igor Mammedov'
> > > Cc: Paolo Bonzini; Jason Wang; Maxime Coquelin; qemu-
> address@hidden;
> > > Michael S . Tsirkin
> > > Subject: RE: [Qemu-devel] [RFC] exec: eliminate ram naming issue as
> > > migration
> > >
> > > Hi Igor and all,
> > >
> > > > -----Original Message-----
> > > > From: Igor Mammedov [mailto:address@hidden
> > > > Sent: Thursday, February 8, 2018 7:30 PM
> > > > To: Tan, Jianfeng
> > > > Cc: Paolo Bonzini; Jason Wang; Maxime Coquelin; qemu-
> > > address@hidden;
> > > > Michael S . Tsirkin
> > > > Subject: Re: [Qemu-devel] [RFC] exec: eliminate ram naming issue as
> > > > migration
> > > >
> > > [...]
> > > > > > It could be solved by adding memdev option to machine,
> > > > > > which would allow to specify backend object. And then on
> > > > > > top make -mem-path alias new option to clean thing up.
> > > > >
> > > > > Do you mean?
> > > > >
> > > > > src vm: -m xG
> > > > > dst vm: -m xG,memdev=pc.ram -object memory-backend-
> > > file,id=pc.ram,size=xG,mem-path=xxx,share=on ...
> > > > Yep, I've meant something like it
> > > >
> > > > src vm: -m xG,memdev=SHARED_RAM -object memory-backend-
> > > file,id=SHARED_RAM,size=xG,mem-path=xxx,share=on
> > > > dst vm: -m xG,memdev=SHARED_RAM -object memory-backend-
> > > file,id=SHARED_RAM,size=xG,mem-path=xxx,share=on
> > >
> > > After a second thought, I find adding a backend for nonnuma pc RAM is
> > > roundabout way.
> > >
> > > And we actually have an existing way to add a file-backed RAM: commit
> > > c902760fb25f ("Add option to use file backed guest memory"). Basically,
> this
> > > commit adds two options, --mem-path and --mem-prealloc, without
> specify
> > > a backend explicitly.
> > >
> > > So how about just adding a new option --mem-share to decide if that's a
> > > private memory or shared memory? That seems much straightforward
> way
> Above options are legacy (which we can't remove for compat reasons),
> their replacement is 'memory-backend-file' backend which has all of
> the above including 'share' property.

OK, such options are legacy. I've no idea of that. Thanks! That makes sense.

> 
> So just add 'memdev' property to machine and reuse memory-backend-file
> with it instead of duplicating functionality in the legacy code.

To "-m" or "-machine"?