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

["Hao, Xudong" <xudong.hao@xxxxxxxxx>]

> -----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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