Re: [RFC] xen/arm: Find automatically the gnttab region for DOM0

[Julien Grall <julien.grall@citrix.com>]

Hi,

On 22/05/2015 01:38, Julien Grall wrote:
> Currently, the grant table region is hardcoded per-platform. When a new
> board is coming up, we have to check the spec in order to find a space
> in the memory layout free. Depending on the platform it may be tedious.
>
> A good candidate for the gnttab region is the one used by Xen binary as
> some part will never be mapped to the DOM0 address, MMIO are mapped 1:1
> and the RAM will be either:
>      - direct mapped: 1:1 mapping is used => no problem
>      - non direct mapped: Xen always relocates himself as high as possible
>      (limited to 4GB on ARM32) and the RAM bank are filled from the first
>      one. It's very unlikely that the gnttab region will overlap with the
>      RAM. Although for safety a check may be necessary when we will reenable
>      the option.
>
> Futhermore, there is plenty of space to contain a big gnttab, the default
> size is 32 frame (i.e 32KB) but it can be changed via a command option.

I miscalculate the size here. It should be 32 * 4KB = 128KB.

Regards,

-- 
Julien Grall