Re: [Xen-devel] Design doc of adding ACPI support for arm64 on Xen - version 2

[Shannon Zhao <zhaoshenglong@xxxxxxxxxx>]

On 2015/8/12 0:01, Julien Grall wrote:
> On 11/08/15 16:19, Ian Campbell wrote:
>>> IIRC we talked about it few months ago and you said that using balloon
>>> page will split in 4K the 1G/2M mapping done in the stage-2 p2m.
>>
>> Did I? Odd because I'm also of the opinion that alloc_ballooned_pages
>> should operate in chunks of 2M at the hypercall layer and keep any
>> resulting spare 4K pages on a free list to use for future such allocations.
> 
> That from what I recall from an IRL talk.
> 
> Anyway, I've looked in my archive to see why we decided to keep the
> grant table parameters (in Xen ACPI table at this point). We were not
> sure that the domain as all the key in hand in order to find memory hole.
> 
> I think it's quite important to not think only about Linux but all other
> Operating Systems. If we ever require a parameters later, it would mean
> that the OS won't be able to run as DOM0 on older Xen.
> 
> Linux is using ballooned page, which means loosing ~128KB (default of
> the grant table on ARM) of memory because we never give back the page to
> Xen due the 1:1 mapping. Although I guess this is not a big deal as it's
> quite small and Linux, as said by David, will support memory hotplug soon.
> 
> FreeBSD is using memory hole in the address space so there is no issue here.
> 
> So I guess we could skip this parameters as 128KB doesn't seem to be a
> big deal.
> 
>> IOW it should avoid such shattering where it can.
> 
> That would work too.
> 

So use xlated_setup_gnttab_pages for both DT and ACPI?

-- 
Shannon


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