Re: [Qemu-devel] [PATCH v18 13/14] memory backend: fill memory backend ram fields

[Igor Mammedov]

On Wed, 26 Feb 2014 13:45:38 +0100
Paolo Bonzini <address@hidden> wrote:

> Il 26/02/2014 13:31, Igor Mammedov ha scritto:
> >> > The problem is that some backends might not be handled the same way.
> >> > For example, not all backends might produce a single void*/size_t pair
> >> > for the entire region.  Think of a "composite" backend that produces a
> >> > large memory region from two smaller ones.
> > I'd prefer to keep backends simple, with 1:1 mapping to memory regions.
> 
> I agree.  However not all backends may have a mapping to a RAM memory 
> region.  A composite backend could create a container memory region 
> whose children are other HostMemoryBackend objects.
> 
> > Is there a need in composite one or something similar?
> 
> I've heard of users that want a node backed partially by hugetlbfs and 
> partially by regular RAM.  Not sure why.
Isn't issue here in how backend is mapped into GPA? Well that is not
backend's job.

Once one starts to put layout (alignment, noncontinuously mapped
memory regions inside of container, ...), mapping HPA->GPA gets complicated.

It would be better to use simple building blocks and model as:
2 separate backends (ram + hugetlbfs) and 2 corresponding DIMM devices.


> 
> Paolo
>