Re: [Embedded-pv-devel] [Xen-devel] [PATCH RFC 00/18] System adjustment to customer needs.

[Andrii Anisov <andrii.anisov@xxxxxxxxxxxxxxx>]

> If I understand correctly, all the initiators but the GPU will be used by
> DOM0 which is already direct mapped. The only issue here is allocating
> memory enough memory below 4GB.
It's not about memory allocation for domain. It is rather about SDRAM
mapping on the bus. J6 has first 2GB for iomems, starting from
0x80000000 2GB of SDRAM mapping plus more SDRAM mapped over 4GB line.
Changing rambase_pfn is painful for J6 release kernel so we just make
it configurable by
    - [PATCH RFC 04/18] libxl: add ability to set rambase_pfn via cfg file.
    - [PATCH RFC 13/18] xen: introduce and use 'dom0_rambase_pfn'
setting for kernel Dom0


> By default Xen will try to allocate as much RAM as possible below 4GB for
> DOM0.

Also we are providing both domains with a piece of non-dma memory for
applications with a patch [PATCH RFC 16/18] xen: Add dom0_mem_high
option & over 4GB memory allocation for Dom0.

> If you are concerned about the amount allocated, you could pre-allocate them 
> before
> hand (such as via the DT as propose in [1]).
I've quickly checked the proposal, looks interesting we would evaluate.

> For the GPU, on another reply you said it was protected by an IPMMU. I
> remembered a series from globallogic to virtualize it in Xen [2]. Can you
> details why this option would not fit in your use case?
> [2]
> http://lists.xenproject.org/archives/html/xen-devel/2014-06/msg03359.html
We have a successor of that patch series. But the GPU MMU is still
32-bit and is not able to address SDRAM mapped over 4GB on the bus.

Andrii Anisov | Associate Manager, Engineering
GlobalLogic
Kyiv, 03038, Protasov Business Park, M.Grinchenka, 2/1
P +38.044.492.9695x3664  M +380505738852  S andriyanisov
www.globallogic.com

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