RE: swiotlb=force in Konrad's xen-pcifront-0.8.2 pvops domU kernel with PCI passthrough

[Dan Magenheimer <dan.magenheimer@oracle.com>]

> From: Keir Fraser [mailto:keir@xen.org]
> Sent: Friday, November 19, 2010 10:58 AM
> To: Dante Cinco; Jeremy Fitzhardinge
> Cc: Xen-devel; mathieu.desnoyers@polymtl.ca; Chris Mason; Andrew
> Thomas; Konrad Rzeszutek Wilk
> Subject: Re: [Xen-devel] swiotlb=force in Konrad's xen-pcifront-0.8.2
> pvops domU kernel with PCI passthrough
> 
> On 19/11/2010 17:52, "Dante Cinco" <dantecinco@gmail.com> wrote:
> 
> > How do I check if rdtsc emulation is on? Does 'xm debug-keys s' do
> it?
> >
> > (XEN) *** Serial input -> Xen (type 'CTRL-a' three times to switch
> > input to DOM0)
> > (XEN) TSC marked as reliable, warp = 0 (count=2)
> > (XEN) dom1: mode=0,ofs=0xca6f68770,khz=2666017,inc=1
> > (XEN) No domains have emulated TSC
> 
> TSC emulation is not enabled.

I *think* "No domains have emulated TSC" will be printed
if there are no domains other than dom0 currently running,
so this may not be definitive.

Also note that tsc_mode=0 means "do the right thing for
this hardware platform" but, if the domain is saved/restored
or live-migrated, TSC will start being emulated. See
tscmode.txt in xen/Documentation for more detail.

Lastly, I haven't tested this code in quite some time,
the code for PV and HVM is different, and I've never
tested it with xl, only with xm.  So bitrot is possible,
though hopefully unlikely.

Thanks,
Dan