Re: [PATCH v2] AMD/IO-APIC: Use old IO-APIC ack method if AMD 813{1, 2} PCI-X tunnel is present

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 05/06/13 09:20, Jan Beulich wrote:
>>>> On 04.06.13 at 18:48, Andrew Cooper <andrew.cooper3@citrix.com> wrote:
>> On 04/06/13 17:29, Jan Beulich wrote:
>>>> +                           "Use ioapic_ack_mode=old\n");
>>> "Don't use \"ioapic_ack=new\"\n" would seem better.
>>>
>>> Jan
>> No - this is more informative to someone who doesn't know the Xen
>> command line arguments inside/out.
> At least the spelling of the option needs to be fixed anyway. And
> the reason I prefer the inverted statement is that if this someone
> adds the suggested option to the beginning of the command line,
> but leaves the bad option in somewhere towards the tail, the bad
> behavior (and the message) will still occur.

I completely missed the spelling - that does need fixing.

While I can appreciate your point of view with the statement, it is only
rare cases where someone would set io_apic_mode anyway and when given
instructions to use =new, can purge instances of =old.

>
> But anyway - I continue to be unconvinced that this case can't be
> easily enough dealt with the admin adding "ioapic_ack=old" to the
> command line.
>
> Jan
>

That describes half the errata workarounds we do.  Why does this deserve
different treatment?.

It can certainly can be worked around by using io_apci_ack=old on the
command line, and that is how we verified the 'fix'.  But in the
meantime it took a normally technically-savvy customer 2 months of time
in highest level support (i.e. my colleagues and I) before we got to the
bottom of the issue.

~Andrew