Subject: Re: [PATCH V11 08/17] powrepc/pci: Refactor pci_dn

From: Bjorn Helgaas <[email-masked]>
Date: Tue, 24 Feb 2015 02:13:30 -0600

On Mon, Feb 23, 2015 at 11:13:49AM +1100, Gavin Shan wrote:
> On Fri, Feb 20, 2015 at 05:19:17PM -0600, Bjorn Helgaas wrote:
> >On Thu, Jan 15, 2015 at 10:27:58AM +0800, Wei Yang wrote:
> >> From: Gavin Shan <[email-masked]>
> >> 
> >> pci_dn is the extension of PCI device node and it's created from
> >> device node. Unfortunately, VFs that are enabled dynamically by
> >> PF's driver and they don't have corresponding device nodes, and
> >> pci_dn. The patch refactors pci_dn to support VFs:
> >> 
> >>    * pci_dn is organized as a hierarchy tree. VF's pci_dn is put
> >>      to the child list of pci_dn of PF's bridge. pci_dn of other
> >>      device put to the child list of pci_dn of its upstream bridge.
> >> 
> >>    * VF's pci_dn is expected to be created dynamically when PF
> >>      enabling VFs. VF's pci_dn will be destroyed when PF disabling
> >>      VFs. pci_dn of other device is still created from device node
> >>      as before.
> >> 
> >>    * For one particular PCI device (VF or not), its pci_dn can be
> >>      found from pdev->dev.archdata.firmware_data, PCI_DN(devnode),
> >>      or parent's list. The fast path (fetching pci_dn through PCI
> >>      device instance) is populated during early fixup time.
> >> 
> >> Signed-off-by: Gavin Shan <[email-masked]>
> >> ---
> >>  arch/powerpc/include/asm/device.h         |    3 +
> >>  arch/powerpc/include/asm/pci-bridge.h     |   14 +-
> >>  arch/powerpc/kernel/pci_dn.c              |  242 ++++++++++++++++++++++++++++-
> >>  arch/powerpc/platforms/powernv/pci-ioda.c |   16 ++
> >>  4 files changed, 270 insertions(+), 5 deletions(-)
> >> ...
> >
> >> +#ifdef CONFIG_PCI_IOV
> >> +static struct pci_dn *add_one_dev_pci_info(struct pci_dn *parent,
> >> +					   struct pci_dev *pdev,
> >> +					   int busno, int devfn)
> >> +{
> >> +	struct pci_dn *pdn;
> >> +
> >> +	/* Except PHB, we always have parent firmware data */
> >> +	if (!parent)
> >> +		return NULL;
> >> +
> >> +	pdn = kzalloc(sizeof(*pdn), GFP_KERNEL);
> >> +	if (!pdn) {
> >> +		pr_warn("%s: Out of memory !\n", __func__);
> >> +		return NULL;
> >> +	}
> >> +
> >> +	pdn->phb = parent->phb;
> >> +	pdn->parent = parent;
> >> +	pdn->busno = busno;
> >> +	pdn->devfn = devfn;
> >> +#ifdef CONFIG_PPC_POWERNV
> >> +	pdn->pe_number = IODA_INVALID_PE;
> >> +#endif
> >> +	INIT_LIST_HEAD(&pdn->child_list);
> >> +	INIT_LIST_HEAD(&pdn->list);
> >> +	list_add_tail(&pdn->list, &parent->child_list);
> >> +
> >> +	/*
> >> +	 * If we already have PCI device instance, lets
> >> +	 * bind them.
> >> +	 */
> >> +	if (pdev)
> >> +		pdev->dev.archdata.firmware_data = pdn;
> >> +
> >> +	return pdn;
> >
> >I'd like to see this done in pcibios_add_device(), as I mentioned in
> >response to "[PATCH V11 01/17] PCI/IOV: Export interface for retrieve VF's
> >BDF".  Maybe that's not feasible for some reason, but it would be a nicer
> >design if it's possible.
> >
> >The remove_dev_pci_info() work would be done in pcibios_release_device()
> >then, of course.
> >
> 
> Yes, it's not feasible. PCI config accessors rely on VF's pci_dn. Before
> calling pcibios_add_device(), we need access VF's config space.  That means
> we need VF's pci_dn before pci_setup_device() as follows:
> 
>     sriov_enable()
>         pcibios_sriov_enable();     /* Currently, VF's pci_dn is created at this point */
>         virtfn_add();
>             virtfn_add_bus();       /* Create virtual bus if necessary */
>                                     /* ---> A */
>             pci_alloc_dev();        /* ---> B */
>             pci_setup_device(vf);   /* Access VF's config space */
>                 pci_read_config_byte(vf, PCI_HEADER_TYPE);
>                 pci_read_config_dword(vf, PCI_CLASS_REVISION);
>                 pci_fixup_device(pci_fixup_early, vf);
>                 pci_read_irq();
>                 pci_read_bases();
>             pci_device_add(vf);
>                 device_initialize(&vf->dev);
>                 pci_fixup_device(pci_fixup_header, vf);
>                 pci_init_capabilities(vf);
>                 pcibios_add_device(vf);
> 
> We have couple of options here:
> 
> 1) Keep current code. VF's pci_dn is going to be destroyed in
>    pcibios_sriov_disable() as we're doing currently.
> 2) Introduce pcibios_iov_virtfn_add() (at A) for platform to override.
>    VF's pci_dn is going to be destroyed in pcibios_release_device().
> 3) Introduce pcibios_alloc_dev() (at B) for platform to override. The
>    VF's pci_dn is going to be destroyed in pcibios_release_device().

Ah, yes, now I see the problem.  I don't really like having to export
pci_iov_virtfn_bus() and pci_iov_virtfn_devfn(), but it's probably not
worth the hassle of changing it, and I think adding more pcibios interfaces
would be even worse.

So let's leave it as-is for now.

> >> +}
> >> +#endif // CONFIG_PCI_IOV
> >> +
> >> +struct pci_dn *add_dev_pci_info(struct pci_dev *pdev, u16 vf_num)
> >> +{
> >> +#ifdef CONFIG_PCI_IOV
> >> +	struct pci_dn *parent, *pdn;
> >> +	int i;
> >> +
> >> +	/* Only support IOV for now */
> >> +	if (!pdev->is_physfn)
> >> +		return pci_get_pdn(pdev);
> >> +
> >> +	/* Check if VFs have been populated */
> >> +	pdn = pci_get_pdn(pdev);
> >> +	if (!pdn || (pdn->flags & PCI_DN_FLAG_IOV_VF))
> >> +		return NULL;
> >> +
> >> +	pdn->flags |= PCI_DN_FLAG_IOV_VF;
> >> +	parent = pci_bus_to_pdn(pdev->bus);
> >> +	if (!parent)
> >>  		return NULL;
> >> -	return PCI_DN(dn);
> >> +
> >> +	for (i = 0; i < vf_num; i++) {
> >> +		pdn = add_one_dev_pci_info(parent, NULL,
> >> +					   pci_iov_virtfn_bus(pdev, i),
> >> +					   pci_iov_virtfn_devfn(pdev, i));
> >> +		if (!pdn) {
> >> +			pr_warn("%s: Cannot create firmware data "
> >> +				"for VF#%d of %s\n",
> >> +				__func__, i, pci_name(pdev));
> >> +			return NULL;
> >> +		}
> >> +	}
> >> +#endif
> >> +
> >> +	return pci_get_pdn(pdev);
> >> +}
> >> +
> >> +void remove_dev_pci_info(struct pci_dev *pdev, u16 vf_num)
> >> +{
> >> +#ifdef CONFIG_PCI_IOV
> >> +	struct pci_dn *parent;
> >> +	struct pci_dn *pdn, *tmp;
> >> +	int i;
> >> +
> >> +	/* Only support IOV PF for now */
> >> +	if (!pdev->is_physfn)
> >> +		return;
> >> +
> >> +	/* Check if VFs have been populated */
> >> +	pdn = pci_get_pdn(pdev);
> >> +	if (!pdn || !(pdn->flags & PCI_DN_FLAG_IOV_VF))
> >> +		return;
> >> +
> >> +	pdn->flags &= ~PCI_DN_FLAG_IOV_VF;
> >> +	parent = pci_bus_to_pdn(pdev->bus);
> >> +	if (!parent)
> >> +		return;
> >> +
> >> +	/*
> >> +	 * We might introduce flag to pci_dn in future
> >> +	 * so that we can release VF's firmware data in
> >> +	 * a batch mode.
> >> +	 */
> >> +	for (i = 0; i < vf_num; i++) {
> >> +		list_for_each_entry_safe(pdn, tmp,
> >> +			&parent->child_list, list) {
> >> +			if (pdn->busno != pci_iov_virtfn_bus(pdev, i) ||
> >> +			    pdn->devfn != pci_iov_virtfn_devfn(pdev, i))
> >> +				continue;
> >> +
> >> +			if (!list_empty(&pdn->list))
> >> +				list_del(&pdn->list);
> >> +			kfree(pdn);
> >> +		}
> >> +	}
> >> +#endif
> >>  }
> >
>