Re: [Xen-devel] [PATCH v2] interrupts: allow guest to set and clear MSI-X mask bit

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Tue, Aug 06, 2013 at 01:17:35PM +0300, Pasi Kärkkäinen wrote:
> On Tue, Aug 06, 2013 at 10:52:58AM +0100, Andrew Cooper wrote:
> > On 06/08/13 09:29, Jan Beulich wrote:
> > >>>> On 05.08.13 at 18:03, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
> > >> On 05/08/13 12:49, Jan Beulich wrote:
> > >>> But a proper solution would of course be preferred. That may involve
> > >>> notifying Xen of the reset from the PF driver.
> > >> That is making the assumption that the PF driver is even aware that the
> > >> reset has occurred.  If the PF driver can get at the reset information,
> > >> I still cant see Xen specific hooks being accepted upstream.
> > > You sort of contradict your earlier statement here that "the VF
> > > requests the PF to reset itself" (where you probably meant "it",
> > > as the VF is hardly allowed to cause a reset of the PF): Such an
> > > operation should imo be visible to the PF driver.
> > >
> > > And then, even if the reset is being done, shouldn't the interrupt
> > > setup occur _after_ the reset? Which would make Xen clear the
> > > flag...
> > 
> > The observed behaviour is this:  On startup, the VF driver issues this
> > backchannel reset of itself (the VF) which, amongst other things, sets
> > the mask bit.  It leaves the MSI/MSI-X addr and data fields alone, but
> > on further consideration, relying on this behaviour might not be a good
> > idea.  The VF is then expected to re-enable the interrupt at its
> > convenience.
> > 
> > There are no obvious hooks in the PF driver to receive notification of
> > these backchannel resets.
> > 
> 
> Doesn't the PF driver log some entries to dom0 kernel dmesg when the VF in 
> domU resets itself? 
> 

At least I've seen such messages from the Intel igxbe PF driver.. or did I 
misunderstand something? 

-- Pasi


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