Re: [Qemu-devel] [PATCH V14 0/3] Virtual Machine Generation ID

[Igor Mammedov <imammedo@redhat.com>]

On Wed, 15 Apr 2015 12:38:57 +0200
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Tue, Mar 03, 2015 at 05:18:12PM +0100, Igor Mammedov wrote:
> > Changes since v13:
> >  * fix comment style to /*... */ in testcase
> >  * make BAR TARGET_PAGE_SIZE as required by spec
> >  * make BAR prefetchable, spec also says that it shouldn't be
> >    marked as non cached
> >  * ACPI part
> >     * merge separate VGID device with PCI device description
> >     * mark device as not shown in UI,
> >       it hides "VM Generation ID" device from device manager
> >       and leaves only "PCI Standard RAM Controller" device there
> 
> In an offline chat, Yan (Cc) mentioned that with windows guests,
> PCI rebalancing can move BAR values around.
> Yan, could you comment on-list please?
> Is there a way to force this, for testing?
> 
> ACPI spec mentions this:
> If a platform uses a PCI BAR Target operation region, an ACPI OS will
> not load a native device driver for the associated PCI function. For
> example, if any of the BARs in a PCI function are associated with a PCI
> BAR Target operation region, then the OS will assume that the PCI
> function is to be entirely under the control of the ACPI BIOS. No driver
> will be loaded. Thus, a PCI function can be used as a platform
> controller for some task (hot-plug PCI, and so on) that the ACPI BIOS
> performs.
It seems that WS2012R2 doesn't honor this part of spec,
it still tries to find matching driver and load it.

> 
> This might also avoid driver prompt from windows?
it isn't.