Re: [Qemu-devel] [PULL for-1.3 0/3] seabios: q35 update

[Gerd Hoffmann]

  Hi,

>>> '-machine q35,diskmode=ahci,ide,raid'? 
>>
>> I'm wondering whenever we want to deal with that at all?
>>
>> "If your guest is too old to handle ahci natively, just stick to piix."
>> is a sensible policy IMHO.
>>
> 
> There was some discussion of trying to make q35 the default for 1.4, in
> which case it may be important to support older OS's such as WinXP.
> 
> Anthony, do you have any opinion on this?

The fundamental issue is that you have either good compatibility (makes
old guests happy) or good performance (makes modern guests happy) by
default.  Picking a default which makes everybody happy is impossible.

That problem doesn't change no matter whenever the choice is piix vs.
q35 or q35+ide vs. q35+ahci.

management apps (using libosinfo) can tackle this in a sensible manner
by picking virtual hardware depending on the guest capabilities.  So I
wouldn't worry too much on qemu level.

>>> 2) HPET ACPI error
>>>
>>> This line: 'IRQNoFlags () {2, 8}' in the HPET acpi table is causing the
>>> folloing ACPI message (removing it makes it go away):
>>
>> Hmm.  That was added to make macos x happy and is also present on real
>> hardware, so I'm wondering what is going on here.
>>
> 
> I also noticed that on Windows 7, the 'IRQNoFlags' line above makes the RTC
> clock complain that it does not have resources available. While removing the
> above line, removes that error.

Hmm.  The IRQNoFlags for the RTC isn't new though, but I can see that
with win7 on piix too.

cheers,
  Gerd