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

["karim.allah.ahmed@xxxxxxxxx" <karim.allah.ahmed@xxxxxxxxx>]

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) ?


> Disabling the 1:1 mapping workaround allocates the region a page at a time so 
> it doesn't suffer from this.
>
> We are probably mostly stuck with this for 4.4. As Julien says for 4.5
> we should probably look into giving dom0 multiple banks where necessary.
>
> Ian.
>
>



-- 
Karim Allah Ahmed.
LinkedIn

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