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

On Sat, May 21, 2016 at 10:32 AM, Julien Grall <julien.grall@xxxxxxx> wrote:
> Hello Meng,

Hi Julien,

> On 20/05/2016 16:21, Meng Xu wrote:
>> On Thu, May 19, 2016 at 5:53 PM, Andrii Anisov
>> <andrii.anisov@xxxxxxxxxxxxxxx> wrote:
>>>>> If the board is not supported by Xen, can we say Xen will support the
>>>>> board with the warkaround?
>>> I would not say boards are supported by XEN (except earlyprintk).
>>> Rather architectures are supported in general, and SoC's are supported
>>> in architecture implementation defined deviations (i.e. SMMU absence).
>> Yes. I searched around for the "Jacinto 6" Automotive processor.[1]
>> It uses Cortex A15 processor...
>> However, I tried the Arndale Octo board two years ago
>> (http://www.arndaleboard.org/wiki/index.php/Main_Page). From my
>> previous experience, the board may not be supported by Xen even though
>> the processor it uses has virtualization extension.. :-(
> It would like to correct you here.

Thank you very much for the correction! :-)

> Xen (and KVM) can run on any board
> providing virtual extensions, a GIC and an architectural timer are
> available.

I see.

> However, some vendor ship boards with a firmware/bootloader that will enter
> the kernel in EL1 rather than EL2 (i.e the hyp mode).

Right! That's exactly what we faced two years ago. :-(

> The bootloader is often U-boot and the upstream version may support the
> board. So if the bootloader is entered in a mode that allows to switch to
> HYP mode (either EL3 or secure EL1), then you can recompile U-boot and flash
> your board. Otherwise, the source may be shipped and you can hack around to
> entered Xen to HYP mode.

Yes. Sometimes, the board needs the signature for the uboot, that's
why we couldn't just compile the source without the manufacturer's
signature two years ago...

Thank you very much for clarifying this. It makes the statement more
precisely. :-)

Best Regards,

Meng Xu
PhD Student in Computer and Information Science
University of Pennsylvania

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