Re: [Qemu-devel] [PATCH 2.1 17/28] memory: move mem_path handling to memory_region_allocate_system_memory

[Paolo Bonzini <pbonzini@redhat.com>]

Il 11/03/2014 04:50, Hu Tao ha scritto:
> On Tue, Mar 04, 2014 at 03:00:45PM +0100, Paolo Bonzini wrote:
>> Like the previous patch did in exec.c, split memory_region_init_ram and
>> memory_region_init_ram_from_file, and push mem_path one step further up.
>> Other RAM regions than system memory will now be backed by regular RAM.
>
> This changes qemu's behaviour regarding using hugetlbfs, especially when
> size of other RAM regions is significant compared to system memory. Will
> this a problem?(compatibilities, user configurations...)

I think it's a bugfix, especially with 1G hugepages.  Wasting 1G on VGA 
memory is not really a good idea.

>>
>> Also, boards that do not use memory_region_allocate_system_memory will
>> not support -mem-path anymore.  This can be changed before the patches
>> are merged by migrating boards to use the function.
>
> IIUC, memory_region_allocate_system_memory() is only called once at
> board initialization time. In most cases, it just works. But there
> are cases that system memory is not initialized by a single call to
> memory_region_allocate_system_memory() that total memory is splitted
> into banks each of which is initialized individually, see
> ppc4xx_sdram_adjust(). How to convert to
> memory_region_allocate_system_memory() in this case? Should we map
> banks into numa nodes?

The solution would be to use aliases to split the system RAM into banks.

Paolo