Re: [Qemu-devel] [Xen-devel] [v5][PATCH 0/5] xen: add Intel IGD passthrough support

[Stefano Stabellini]

On Tue, 1 Jul 2014, Michael S. Tsirkin wrote:
> On Mon, Jun 30, 2014 at 03:31:05PM -0400, Ross Philipson wrote:
> > On 06/30/2014 03:22 PM, Stefano Stabellini wrote:
> > >On Mon, 30 Jun 2014, Michael S. Tsirkin wrote:
> > >>On Mon, Jun 30, 2014 at 03:24:58PM +0800, Chen, Tiejun wrote:
> > >>>On 2014/6/30 14:48, Michael S. Tsirkin wrote:
> > >>>>On Mon, Jun 30, 2014 at 10:51:49AM +0800, Chen, Tiejun wrote:
> > >>>>>On 2014/6/26 18:03, Paolo Bonzini wrote:
> > >>>>>>Il 26/06/2014 11:18, Chen, Tiejun ha scritto:
> > >>>>>>>
> > >>>>>>>>
> > >>>>>>>>- offsets 0x0000..0x0fff map to configuration space of the host MCH
> > >>>>>>>>
> > >>>>>>>
> > >>>>>>>Are you saying the config space in the video device?
> > >>>>>>
> > >>>>>>No, I am saying in a new BAR, or at some magic offset of an existing
> > >>>>>>MMIO BAR.
> > >>>>>>
> > >>>>>
> > >>>>>As I mentioned previously, the IGD guy told me we have no any unused a
> > >>>>>offset or BAR in the config space.
> > >>>>>
> > >>>>>And guy who are responsible for the native driver seems not be accept 
> > >>>>>to
> > >>>>>extend some magic offset of an existing MMIO BAR.
> > >>>>>
> > >>>>>In addition I think in a short time its not possible to migrate i440fx 
> > >>>>>to
> > >>>>>q35 as a PCIe machine of xen.
> > >>>>
> > >>>>That seems like a weak motivation.  I don't see a need to get something
> > >>>>merged upstream in a short time: this seems sure to miss 2.1,
> > >>>>so you have the time to make it architecturally sound.
> > >>>>"Making existing guests work" would be a better motivation.
> > >>>
> > >>>Yes.
> > >>
> > >>So focus on this then. Existing guests will probably work
> > >>fine on a newer chipset - likely better than on i440fx.
> > >>xen management tools need to do some work to support this?
> > >
> > >Unfortunately existing Windows guests don't take well chipset changes.
> > >Windows might request a new activation.
> > 
> > That is a very good point. A while back I did a bunch of work to try to keep
> > Windows activated between running an instance of Windows on bare metal and
> > as a VM. There were numerous bits of hardware and firmware that went into
> > the calculation as to whether Windows thought it was the same platform for
> > activation purposes. Changing the chipset sounds like a likely candidate for
> > inspection. Somewhere out there on the webs is a partial list of the things
> > that are inspected - lost the URL.
> 
> It's not hard to try it out with kvm (you just need to remember to use ide 
> with
> q35: ahci is the default there).  I did, and windows did not ask me to
> re-activate.
> 
> The detailed info is not hard to find:
> http://en.wikipedia.org/wiki/Microsoft_Product_Activation
> links to:
> http://technet.microsoft.com/en-us/library/bb457054.aspx
> 
> 
> 1
> Display Adapter
> 00010 (5)
> 2
> SCSI Adapter
> 00011 (5)
> 3
> IDE Adapter
> 0011 (4)
> 4
> Network Adapter MAC Address
> 1001011000 (10)
> 5
> RAM Amount Range (i.e. 0-64mb, 64-128mb, etc)
> 101 (3)
> 6
> Processor Type
> 011 (3)
> 7
> Processor Serial Number
> 000000 (6)
> 8
> Hard Drive Device
> 1101100 (7)
> 9
> Hard Drive Volume Serial Number
> 1001000001 (10)
> 10
> CD—ROM / CD-RW / DVD-ROM
> 010111 (6)
> -
> "Dockable"
> 0 (1)
> -
> Hardware Hash version (version of algorithm used)
> 001 (3)
> 
> So no, chipset version won't cause re-activation.

The page you linked is about Windows XP. Newer Windows versions have
stricter activation rules.  I don't think that moving existing VM images
from piix to q35 could be done without extensive testing of all the
major existing operating system images. I certainly wouldn't rely on a
wikipedia page for this.

Also I don't like the idea of tying Tiejun's patch series, that covers a
very narrow use case, to something as important and general purpose as
upgrading chipset.