Re: [Xen-devel] Patches for stable

[Juergen Gross <jgross@xxxxxxxx>]

On 05/04/18 15:42, George Dunlap wrote:
> On Thu, Apr 5, 2018 at 2:06 PM, Juergen Gross <jgross@xxxxxxxx> wrote:
>> On 05/04/18 15:00, Boris Ostrovsky wrote:
>>> On 04/05/2018 08:19 AM, Juergen Gross wrote:
>>>> On 05/04/18 12:06, George Dunlap wrote:
>>>>
>>>>> Aren't there flags in the binary somewhere that could tell the
>>>>> toolstack / Xen whether the kernel in question needs the RSDP table in
>>>>> lowmem, or whether it can be put higher?
>>>> Not really. Analyzing the binary whether it accesses the rsdp_addr in
>>>> the start_info isn't the way to go, IMO.
>>>>
>>>> I've sent a patch to xen-devel adding a quirk flag to the domain's
>>>> config to enable the admin special casing such an "old" kernel.
>>>
>>> Can we backport latest struct hvm_start_info changes (which bumped
>>> interface version) to 4.11 and pass RSDP only for versions >=1?
>>
>> And this would help how?
>>
>> RSDP address is passed today, the kernel just doesn't read it. And
>> how should Xen know which interface version the kernel is supporting?
>> And Xen needs to know that in advance in order to place the RSDP in
>> low memory in case the kernel isn't reading the RSDP address from
>> start_info.
> 
> But the kernel image has ELF notes, right?  You can put one that
> indicates that this binary *does* know how to read the RSDP from the
> start_info, and if you don't find that, put it in lowmem.

Sow you would hurt BSD which does read the RSDP address correctly but
(today) has no such ELF note.

I think extending the PVH interface in such a way is no good idea.


Juergen


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