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Re: [Xen-devel] Detecting PV drivers

On 04/04/13 17:30, Jon Ludlam wrote:
> Hi,
> I'm trying find out the best way of detecting whether PV drivers have 
> loaded in an HVM guest. For example, this is so we can decide whether or 
> not to wait for a response from the guest when suspending.
> I think the best way of doing this is to find out whether the hypercall 
> page has been populated or not, as this is the first thing that any PV 
> drivers will have to do, but I don't know how to detect this, or even if 
> this is possible - is there any way of finding this out?

Not currently as far as I can tell, but intercepting
hvm_hypercall_page_initialise() and setting a boolean in struct domain
would be easy.

The better question would be how to get this information out of Xen.

Given that the memory claim hypercall has already bumped the hypercall
interface version, would it be acceptable to have another change to
struct xen_domctl_getdomaininfo ?


> At the moment we're currently thinking of looking at status of the 
> callback IRQ, which is the second thing that the Citrix PV drivers 
> currently do, but I'm not sure about any other drivers. Would this be a 
> reasonable thing to do if we can't detect the hypercall page?
> Cheers,
> Jon
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