Re: [Xen-devel] [PATCH V4] xen/arm: domain_build: allocate lowmem for dom0 as much as possible

[Peng Fan <van.freenix@xxxxxxxxx>]

Hi Julien,

Sorry for late reply.

On Tue, Nov 01, 2016 at 02:42:06PM +0000, Julien Grall wrote:
>Hi Peng,
>
>Sorry for the late answer.
>
>On 23/09/2016 03:55, Peng Fan wrote:
>>On AArch64 SoCs, some IPs may only have the capability to access
>>32 bits address space. The physical memory assigned for Dom0 maybe
>>not in 4GB address space, then the IPs will not work properly.
>>So need to allocate memory under 4GB for Dom0.
>>
>>There is no restriction that how much lowmem needs to be allocated for
>>Dom0 ,so allocate lowmem as much as possible for Dom0.
>>
>>This patch does not affect 32-bit domain, because Variable "lowmem" is
>>set to true at the beginning. If failed to allocate bank0 under 4GB,
>>need to panic for 32-bit domain, because 32-bit domain requires bank0
>>be allocated under 4GB.
>>
>>For 64-bit domain, set "lowmem" to false, and continue allocating
>>memory from above 4GB.
>>
>>Signed-off-by: Peng Fan <peng.fan@xxxxxxx>
>>Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>>Cc: Julien Grall <julien.grall@xxxxxxx>
>
>Reviewed-by: Julien Grall <julien.grall@xxxxxxx>
>
>I am undecided whether this should be considered as a bug fix for Xen 4.8.
>Are you aware of any ARM64 platform we currently support requiring allocation
>of memory below 4GB?

I have no idea about this (:, but I think this is a bug fix. Alought current
supported platforms works well, users may choose 4.8 to support their
new platform which has the limitation to access 64bit address.

Regards,
Peng.

>
>Regards,
>
>-- 
>Julien Grall

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