Preventing hotplug devices in HVM guests

Preventing hotplug devices in HVM guests

[Matthew Hook]

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Hi there,

Is there a way to prevent Windows HVM guests from seeing passed through
devices like graphics cards as being ejectable?
i.e. you pass through a graphics adapter to an HVM guest which happens to
be Windows.  Windows sees this as a device with hotplug capability.
Therefore it shows up in "safely remove hardware" option in the windows
system tray.

VMWare provides an option to turn that off.
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1012225

I don't seem an option of this in Xen 4.2 yet.  How can I override
this behavior in Xen?

I tried commenting out the following in:  tools/ioemu-qemu-xen/hw$ vi
pass-through.c

    /* SHPC Capability List Item reg group */
    {
        .grp_id     = PCI_CAP_ID_HOTPLUG,
        .grp_type   = GRP_TYPE_HARDWIRED,
        .grp_size   = 0x08,
        .size_init  = pt_reg_grp_size_init,
    },

but that didn't seem to do it.

Matt

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Re: Preventing hotplug devices in HVM guests

[Ian Campbell]

On Thu, 2012-03-01 at 01:32 +0000, Matthew Hook wrote:
> Hi there,
> 
> 
> Is there a way to prevent Windows HVM guests from seeing passed
> through devices like graphics cards as being ejectable?
> i.e. you pass through a graphics adapter to an HVM guest which happens
> to be Windows.  Windows sees this as a device with hotplug capability.
> Therefore it shows up in "safely remove hardware" option in the
> windows system tray.
> 
> 
> VMWare provides an option to turn that off.
> http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1012225
> 
> 
> I don't seem an option of this in Xen 4.2 yet.  How can I override
> this behavior in Xen?

A total stab in the dark but perhaps you need to fiddle with the ACPI
tables? Not sure but maybe in tools/firmware/hvmloader/acpi/mk_dsdt.c
where the PCI slots are defined? In particular the _STA and _EJ0 methods
seems to imply hotplug support to me. I'm afraid you'd probably need to
read the ACPI spec to be sure of their meaning though :-(

Ian.