Re: [Xen-users] GPLPV, clock drift and PVUSB in Windows XP HVM

[Eric Lindsey <eslindsey@xxxxxxxxx>]

I'm sorry for being unclear in my original message. I'm experiencing the clock 
drift with and without the GPLPV drivers. However, I was surprised that those 
drivers didn't include their own version of Linux's independent_wallclock, 
which I presume takes care of the clock drift problem in those operating 
systems (though I'll be the first to admit that's merely an assumption and I've 
very little experience in this area). How can I solve the clock drift problem, 
and keep my XP HVM synchronized with my dom0 hardware clock (which does not 
suffer from drift)? 

The info on the /nogplpv switch is useful; I'm surprised it isn't documented 
somewhere more obvious than what I could find with a Google search. 

Thanks for the reply, James! 

On Jun 29, 2012, at 3:18 AM, James Harper <james.harper@xxxxxxxxxxxxxxxx> wrote:

>> 
>> 1. Shouldn't the GPLPV drivers take care of the (bad) clock drift I'm
>> experiencing in my Windows XP HVM? Or is there some other way around
>> this problem that I haven't been able to find on Google? How can I tell if 
>> the
>> GPLPV drivers are active? I've added the /gplpv switch to the boot.ini file 
>> and
>> the virtual NIC is definitely using the GPLPV version but other than that I'm
>> not sure how to tell.
> 
> You don't need to use any switches to make gplpv active. You can use the 
> /nogplpv switch to make it inactive if required for testing, but that only 
> deactivates the vbd and vif drivers.
> 
> GPLPV won't (shouldn't) have any impact on clock drift. If you only get clock 
> drift when running with GPLPV then let me know.
> 
>> 2. On this same Windows XP HVM, I'd like to experiment with the PVUSB 2.0
>> pass thru. My server (Dell PowerEdge 2900) does NOT support IOMMU so it
>> can't be hardware. I've read that the PVUSB performance is up to about 60%
>> of native 2.0, but still better than the qemu 1.1 pass thru. Unfortunately, I
>> can't find any documentation online about how to actually use it. Currently I
>> have these lines in my .cfg file:
>> usb = 1
>> usbdevice = 'tablet'
>> usbdevice = 'host:xxxx:yyyy'
>> Obviously I would need to remove the host: line to free up the device from
>> qemu pass thru so I can use PVUSB pass thru instead, but after that I'm not
>> sure what commands to issue or put in the domain's .cfg file.
>> P.S. I did choose to install PvUsb when installing GPLPV so I'm assuming 
>> that's
>> all I need to do on the domU end.
>> 
> 
> You need to make sure you have usb backend drivers in your dom0, then you use 
> xm to add host controllers and devices. Google for usb-hc-create and you 
> should find some info.
> 
> James

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