Re: [Xen-devel] [RFC PATCH] xen/x86: Increase xen_e820_map to E820_X_MAX possible entries

[Juergen Gross <jgross@xxxxxxxx>]

On 15/11/16 08:15, Jan Beulich wrote:
>>>> On 15.11.16 at 07:33, <JGross@xxxxxxxx> wrote:
>> On 15/11/16 01:11, Alex Thorlton wrote:
>>> Hey everyone,
>>>
>>> We're having problems with large systems hitting a BUG in
>>> xen_memory_setup, due to extra e820 entries created in the
>>> XENMEM_machine_memory_map callback.  The change in the patch gets things
>>> working, but Boris and I wanted to get opinions on whether or not this
>>> is the appropriate/entire solution, which is why I've sent it as an RFC
>>> for now.

>> While I think extending the e820 table is the right thing to do I'm
>> questioning the assumptions here.
>>
>> Looking briefly through the Xen hypervisor sources I think it isn't
>> yet ready for such large machines: the hypervisor's e820 map seems to
>> be still limited to 128 e820 entries. Jan, did I overlook an EFI
>> specific path extending this limitation?
> 
> No, you didn't. I do question the correlation with "large machines"
> here though: The issue isn't with large machines afaict, but with
> ones having very many entries (i.e. heavily fragmented).

Alex, I would appreciate if you could send me the E820 map printed
at a bare metal Linux boot. I suspect it is already larger than
128 entries and the hypervisor is just cutting it off at the end.


Juergen

Removed all but Xen guys from CC list

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