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

From: Gavin Shan <[email-masked]>
Date: Mon, 23 Feb 2015 11:13:49 +1100

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().

Thanks,
Gavin

>> +}
>> +#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
>>  }
>