Hmm, you are right. I have found that WinXP and Win7 could not handle the VGA remove sci interrupt. Please try to execute "xm pci-detach Domain 00:00:02.0". So I directly invoke acpi_php_writeb to handle VGA remove event.

2010/6/4 Stefano Stabellini <stefano.stabellini@eu.citrix.com>
On Fri, 4 Jun 2010, ÓڼѸû wrote:
>
> Hi,
>
> I want to switch video card live between two HVMs. My simplest idea is that when the HVM has the permission to access
> passthrough video card, and another HVM will be paused. If switch from A to B, execute commands :
>
> xm pause A ;
>
> xm pci-detach A  00:00:02.0 ;
>
> xm pci-attach B 00:00:02.0 ;
>
> xm unpause B.
>
>  
>
> I have a try, but failed. The pseudo-code is as below. Can you give me some ideas? Any suggestions will be thankful.
>

pci-detach needs cooperation from the guest, how the guest is supposed
to handle the acpi interrupt if it is paused?