Re: [Qemu-devel] [PATCH 02/15] xen: Add xen_machine_fv

[Kevin Wolf <kwolf@redhat.com>]

Am 16.08.2010 16:38, schrieb Anthony Liguori:
> On 08/16/2010 09:13 AM, Kevin Wolf wrote:
>> Am 16.08.2010 16:04, schrieb Stefano Stabellini:
>>    
>>> On Mon, 16 Aug 2010, Kevin Wolf wrote:
>>>      
>>>> Am 12.08.2010 16:09, schrieb stefano.stabellini@eu.citrix.com:
>>>>        
>>>>> From: Anthony PERARD<anthony.perard@citrix.com>
>>>>>
>>>>> Add the Xen FV (Fully Virtualized) machine to Qemu;
>>>>> this is groundwork to add Xen device model support in Qemu.
>>>>>
>>>>> Signed-off-by: Anthony PERARD<anthony.perard@citrix.com>
>>>>> Signed-off-by: Stefano Stabellini<stefano.stabellini@eu.citrix.com>
>>>>>          
>>>> Why does this need its own machine type? Shouldn't an HVM machine really
>>>> look like a PC? And indeed most of this code looks like a (slightly
>>>> outdated) copy of pc_piix.c with !pci_enabled code paths removed.
>>>>        
>>>
>>> The main reason is that we need some xen specific initializations, as you can
>>> see from xen_init_fv.
>>>      
>> Right, there are some more Xen specific things added later. However, the
>> main part of it is duplicated from pc_piix.c. I'm sure that with some
>> refactoring we could call these functions instead of copying and
>> modifying them. The problem with the latter is that they will inevitably
>> diverge even for changes that make sense for both.
>>
>> I'm not even sure that the machine is the right place to do these Xen
>> specific initializations (expect for the Xen platform PCI device). As
>> far as I understand, the QEMUMachine is considered guest state whereas
>> most of these initializations concern host state.
>>    
> 
> To be honest, I think we'll need KVM, Xen, and QEMU specific machines.
> 
> The right default set of hardware for all three is different.

Right, I agree. This is why I put the exception for the platform device.
There are probably some more devices for which the same applies.

But these exceptions all about guest state. If qdev was finished, this
would be a matter of having a different configuration file, right?

This series, as I understand it, is adding much more to the Xen FV
machine. Things that are not about which devices a VM contains, but
about some implementation details of the host.

Kevin