linux-kernel - Re: [RFC/RFT PATCH v2 3/3] PCI/ACPI: Add ACPI pci_bus_find_numa

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Message-ID: <20170517160424.GA8643@red-moon>
Date:   Wed, 17 May 2017 17:04:24 +0100
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Robert Richter <robert.richter@...ium.com>
Cc:     linux-pci@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
        Sergey Temerkhanov <s.temerkhanov@...il.com>,
        Sinan Kaya <okaya@...eaurora.org>,
        Zhou Wang <wangzhou1@...ilicon.com>,
        Vadim Lomovtsev <Vadim.Lomovtsev@...iumnetworks.com>
Subject: Re: [RFC/RFT PATCH v2 3/3] PCI/ACPI: Add ACPI
 pci_bus_find_numa_node() implementation

On Wed, May 17, 2017 at 04:35:58PM +0200, Robert Richter wrote:
> On 17.05.17 14:46:54, Lorenzo Pieralisi wrote:
> 
> > More explicitly, I think the whole series should work also with the diff
> > below applied on top of it. Side note: for consistency, I do not think
> > that adding a DT counterpart to pci_bus_find_numa_node() would hurt.
> > 
> > Thanks !
> > Lorenzo
> > 
> > -- >8 --
> > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> > index 76c089f..cf0692c 100644
> > --- a/drivers/pci/probe.c
> > +++ b/drivers/pci/probe.c
> > @@ -862,7 +862,7 @@ static struct pci_bus *pci_alloc_child_bus(struct pci_bus *parent,
> >  	 */
> >  	child->dev.class = &pcibus_class;
> >  	dev_set_name(&child->dev, "%04x:%02x", pci_domain_nr(child), busnr);
> > -	set_dev_node(&child->dev, dev_to_node(&parent->dev));
> > +
> 
> Hmm, in device_add() there is already:
> 
> 	/* use parent numa_node */
> 	if (parent && (dev_to_node(dev) == NUMA_NO_NODE))
>         	set_dev_node(dev, dev_to_node(parent));
> 
> So there are cases where the device has a different node than the
> parent. I am not sure if we can assume for pci that it maps always.
> 
> And since device_add() is called later anyway, the above change might
> not necessary at all.

That's why I _removed_ the set_dev_node() in the diff above (that applies
to patch (2)), I do not think it is a) correct and b) necessary to
propagate the NUMA node from bus to a child bus given that device_add()
takes care of that already.

I should post a v3 (with the diff above applied) so that we are all on
the same page and we can test it.

> But at least we must assign the node id to the
> bridge, which is the parent. Maybe just have in
> acpi_pci_root_create():
> 
> 	bridge = get_device(bus->bridge);
> 	adev = to_acpi_device_node(bridge->fwnode);
> 	set_dev_node(bridge, acpi_get_node(adev->handle));

I do not think that's enough, I need to check again but I think that
also the bus->dev should have its NUMA node set for things to work (and
allow the NUMA node to propagate correctly through device_add())
otherwise pcibus_to_node() would fail for devices sitting on the root
bus, right ?

I will check again and post v3 shortly.

Thanks !
Lorenzo

> 
> -Robert
> 
> 
> >  	/*
> >  	 * Set up the primary, secondary and subordinate
> >  	 * bus numbers.