Re: [Xen-devel] XEN[ARM] Master not working on Allwinner A20

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 01/07/2014 02:31 PM, karim.allah.ahmed@xxxxxxxxx wrote:
> On Tue, Jan 7, 2014 at 1:58 PM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
>> On Sun, 2014-01-05 at 16:48 +0000, karim.allah.ahmed@xxxxxxxxx wrote:
>>
>>> If you still can't boot with any memory bigger than 128M, as a fast
>>> workaround you can apply this patch.
>>
>> I wonder if it might be possible to work around this by more carefully
>> selecting the load addresses for Xen+Linux+DTB+initrd, such that they
>> are packed into the top end of RAM, leaving a larger contiguous chunk
>> available at the beginning. e.g. if sizeof(Xen)=X and sizeof(Linux)=L
>> and sizeof(DTB)=D (all rounded up to 2M boundary) then load things at:
>>         MEMMAX-X:       Leave free for high relocation of hypervisor
>>         MEMMAX-X-L:     Load Linux here
>>         MEMMAX-X-L-D:   Load DTB here
>>         MEMMAX-X-L-D-X: Load initial Xen image here
>>
>> Ultimately this is because allocations need to be aligned to their size,
>> so on a 1GB system there are only two possible 512MB allocations, if
>> even one page is allocated in each half then it isn't possible to
>> satisfy things. I don't think the core allocator gives us the option to
>> do non-aligned allocations.
> 
> What if we allocated the dom0 from the boot allocator instead (before
> ditching it) ?

If I remembered correctly, Anthony did this kind of modification for the
first port of Xen on the Arndale.

It's a too intrusive in the code. As I said previously, the best
solution is having multiple bank support for dom0. It will take you less
time to wrote a such patch.

-- 
Julien Grall

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