Re: [Qemu-devel] [PATCH RFC 1/2] memory: make MemoryRegion alias migratable

[Igor Mammedov <imammedo@redhat.com>]

On Tue, 30 Jul 2019 15:34:54 +0200
Paolo Bonzini <pbonzini@redhat.com> wrote:

> On 30/07/19 15:25, Igor Mammedov wrote:
> > I'd guess you've meant RAMBlocks instead of memory regions, if that's it
> > then yes, every alias pointing to RAM backed memory region will have
> > RAMBlock that's points to aliased part of aliased memory region.
> 
> The question is just, does it break migration from old QEMU to new QEMU
> on x86 (which has plenty of RAM-backed aliases)?  If not, explain that
> in the commit message or in a code comment.

pc/q35 old<->new new<->old ping pong tests worked fine (qemu with default devices).

My understanding was that one needs to call vmstate_register_ram()
to make memory region migratable, which marks specific RAMBlock
as migratable. So just assigning new RAMBlock to mr->ram_block shouldn't
affect migration, unless vmstate_register_ram() is called on alias.

I'll add it to commit message.

> 
> Paolo
>