Re: [Xen-devel] Detecting PV drivers

[Jonathan Ludlam <Jonathan.Ludlam@xxxxxxxxxxxxx>]

Excellent, in that case if we do this in the short term then we'll be 
consistent with the behaviour when we switch to using libxl later.

Should have looked there first, really. Apologies.

Jon

Sent from my iPad

On 5 Apr 2013, at 11:14, "Stefano Stabellini" 
<stefano.stabellini@xxxxxxxxxxxxx> wrote:

> On Thu, 4 Apr 2013, 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?
>> 
>> 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?
> 
> This is exactly what libxl does right now, see:
> 
> tools/libxl/libxl_dom.c:libxl__domain_suspend_common_callback
> 
> Libxl also checks the state of HVM_PARAM_ACPI_S_STATE.

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