Re: [Qemu-devel] [PATCH v2 4/4] ioh3420: Enable ARI forwarding

[Michael S. Tsirkin]

On Mon, Aug 25, 2014 at 11:13:01AM +0200, Knut Omang wrote:
> On Mon, 2014-08-25 at 06:09 +0000, Gonglei (Arei) wrote:
> > > From: Michael S. Tsirkin [mailto:address@hidden
> > > Subject: Re: [PATCH v2 4/4] ioh3420: Enable ARI forwarding
> > > 
> > > On Sun, Aug 24, 2014 at 03:32:20PM +0200, Knut Omang wrote:
> > > > Signed-off-by: Knut Omang <address@hidden>
> > > 
> > > BTW pcie_cap_is_arifwd_enabled is still unused.
> > 
> > Not yet, but I have posted a patch series:
> > 
> > [PATCH v2 0/2] add check for PCIe root ports and downstream ports
> > 
> > Which we used this function to check ARI Forwarding is enabled or not.
> > I hope you can help me review it, thanks a lot!
> > 
> > BTW, I will rebase my patches on Kunt's patch series. And will do some 
> > fixes 
> > about Hu Tao's and Marcel Apfelbaum's comments.
> > 
> > > We really should use it to make ARI work properly, right?
> > > 
> > Yes. I think we should.
> 
> Modelling the real world, one way to go with multifunction devices would
> be to introduce a separate concept of a "PCIFunction" object in the
> current Qemu model, and let each device have 1 or more such function
> objects associated with them. 
> 
> The simpler way to implement a true multifunction device would just be
> to add one PCIDevice object at the right bus, devfn for each additional
> function that are associated with the master device. 
> 
> I have implemented the latter approach in a simple SR/IOV emulation
> implementation - will post a patch for that shortly, as it seems to be
> relevant for this discussion.
> 
> With that approach (which came out pleasantly simple wrt changes in the
> code) the role of the ARI forwarding bit would be to do nothing when
> enabled, as ARI forwarding works with no changes, but make ARI
> forwarding, when disabled or not available, makes the additional
> functions beyond #8 not addressable from the outside (which in my view
> is what a modified version of Gonglei's patch should do)
> 
> Knut

Makes sense to me.

> > Best regards,
> > -Gonglei
> > 
> > > > ---
> > > >  hw/pci-bridge/ioh3420.c | 2 ++
> > > >  1 file changed, 2 insertions(+)
> > > >
> > > > diff --git a/hw/pci-bridge/ioh3420.c b/hw/pci-bridge/ioh3420.c
> > > > index e6674a1..cce2fdd 100644
> > > > --- a/hw/pci-bridge/ioh3420.c
> > > > +++ b/hw/pci-bridge/ioh3420.c
> > > > @@ -85,6 +85,7 @@ static void ioh3420_reset(DeviceState *qdev)
> > > >      pcie_cap_root_reset(d);
> > > >      pcie_cap_deverr_reset(d);
> > > >      pcie_cap_slot_reset(d);
> > > > +    pcie_cap_arifwd_reset(d);
> > > >      pcie_aer_root_reset(d);
> > > >      pci_bridge_reset(qdev);
> > > >      pci_bridge_disable_base_limit(d);
> > > > @@ -119,6 +120,7 @@ static int ioh3420_initfn(PCIDevice *d)
> > > >          goto err_msi;
> > > >      }
> > > >
> > > > +    pcie_cap_arifwd_init(d);
> > > >      pcie_cap_deverr_init(d);
> > > >      pcie_cap_slot_init(d, s->slot);
> > > >      pcie_chassis_create(s->chassis);
> > > > --
> > > > 1.9.0
> > 
>