Re: [Xen-devel] [PATCH v2] Re-enable LTR/OBFF when device is owned by pciback

["Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx>]

> -----Original Message-----
> From: Konrad Rzeszutek Wilk [mailto:konrad.wilk@xxxxxxxxxx]
> Sent: Wednesday, May 23, 2012 4:34 AM
> To: Zhang, Xiantao
> Cc: Hao, Xudong; Jan Beulich; xen-devel
> Subject: Re: [Xen-devel] [PATCH v2] Re-enable LTR/OBFF when device is
> owned by pciback
> 
> On Tue, May 22, 2012 at 01:57:44AM +0000, Zhang, Xiantao wrote:
> > Hi, Jan/Konrad
> >    Do you have further comments about this patch ?   Thanks!
> 
> Well .. What about making this be in the generic code? That way both KVM
> and Xen can benefit? And also then the default values don't have to show up
> in two places.

Good point! Maybe we can merge the implementations for Xen and KVM, and 
pci-stub driver maybe the proper place for accommodating such logic, I think.  
Thanks!  
Xiantao



> > Xiantao
> >
> > > -----Original Message-----
> > > From: Hao, Xudong
> > > Sent: Wednesday, May 09, 2012 2:26 PM
> > > To: Jan Beulich; Konrad Rzeszutek Wilk
> > > Cc: xen-devel; Zhang, Xiantao
> > > Subject: RE: [Xen-devel] [PATCH v2] Re-enable LTR/OBFF when device
> > > is owned by pciback
> > >
> > > > -----Original Message-----
> > > > From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> > > > Sent: Tuesday, May 08, 2012 5:42 PM
> > > > To: Hao, Xudong; Konrad Rzeszutek Wilk
> > > > Cc: xen-devel
> > > > Subject: Re: [Xen-devel] [PATCH v2] Re-enable LTR/OBFF when device
> > > > is owned by pciback
> > > >
> > > > >>> On 08.05.12 at 11:05, "Hao, Xudong" <xudong.hao@xxxxxxxxx>
> wrote:
> > > > >>  -----Original Message-----
> > > > >> From: Konrad Rzeszutek Wilk [mailto:konrad.wilk@xxxxxxxxxx] On
> > > > >> Sun, May 06, 2012 at 07:35:47AM +0000, Hao, Xudong wrote:
> > > > >> > > From: Konrad Rzeszutek Wilk [mailto:konrad.wilk@xxxxxxxxxx]
> > > > >> > > Don't you need to disable this when the device is
> > > > >> > > un-assigned from the
> > > > >> guest?
> > > > >> > >
> > > > >> >
> > > > >> > I don't think this need to be disabled when device is
> > > > >> > un-assigned from
> > > > > guest.
> > > > >> If host want to use device again, the host device driver need
> > > > >> re-load, so whether disabling ltr/obff is up to host device driver.
> > > > >>
> > > > >> What if the driver isn't doing that?
> > > > >
> > > > > Make it clear, here host side do not be considered, host has its
> > > > > own
> > > driver.
> > > > > The only thing is to make sure ltr/obff is enabled before
> > > > > assigning guest, so that benefit on power.
> > > > >
> > > > > Since device is owned by pciback again when it un-assigned from
> > > > > guest, we need not disable explicitly.
> > > >
> > > > As you didn't answer my respective earlier question - _if_ this is
> > > > a feature needing enabling (and parameter tweaking), I'd imply
> > > > there are possible incompatibilities (i.e. reasons for not
> > > > enabling this always), and hence this shouldn't be done
> > > > universally (and with fixed values for the parameters) _and_ should be
> properly reset.
> > > >
> > > Only Xen administrator can hide a device by pciback, and can assign
> > > a device to guest. These power feature such as ltr and obff should
> > > be enabled by a sys-admin, I do not know which situation is a
> > > possible disabling these features, and why sys-admin want to disable
> them?

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