Re: [PATCH 1/2 V3] PCI: introduce device assignment interface and refactory related code

Alex Williamson
2014-07-11T15:25:10Z

On Fri, 2014-07-11 at 23:19 +0800, Ethan Zhao wrote:
>
> > 在 2014年7月11日，下午10:54，Alex Williamson <alex.williamson@redhat.com> 写道：
> >
> >> On Fri, 2014-07-11 at 22:37 +0800, Ethan Zhao wrote:
> >>
> >>>> 在 2014年7月11日，下午10:15，Alex Williamson <alex.williamson@redhat.com> 写道：
> >>>>
> >>>>> On Fri, 2014-07-11 at 07:13 -0600, Alex Williamson wrote:
> >>>>> On Fri, 2014-07-11 at 20:30 +0800, Ethan Zhao wrote:
> >>>>> This patch introduces two new device assignment functions
> >>>>>
> >>>>> pci_iov_assign_device(),
> >>>>> pci_iov_deassign_device()
> >>>>>
> >>>>> along with the existed one
> >>>>>
> >>>>> pci_vfs_assigned()
> >>>>>
> >>>>> They construct the VFs assignment management interface, used to assign/
> >>>>> deassign device to VM and query the VFs reference counter. instead of
> >>>>> direct manipulation of device flag.
> >>>>>
> >>>>> This patch refashioned the related code and make them atomic.
> >>>>>
> >>>>> v3: change the naming of device assignment helpers, because they work
> >>>>> for all kind of PCI device, not only SR-IOV (david.vrabel@citrix.com)
> >>>>>
> >>>>> v2: reorder the patchset and make it bisectable and atomic, steps clear
> >>>>> between interface defination and implemenation according to the
> >>>>> suggestion from alex.williamson@redhat.com
> >>>>>
> >>>>> Signed-off-by: Ethan Zhao <ethan.zhao@oracle.com>
> >>>>> ---
> >>>>
> >>>> - Use a cover patch to describe the series
> >>>>
> >>>> - Version information goes here, below the "---", not above it
> >>>>
> >>>> - I stand by the patch breakdown I suggested originally, there are too
> >>>> many logical changes here in patch 1. There are easily 3 separate
> >>>> patches here.
> >>>>
> >>>> - Renaming s/sriov/iov/ doesn't address the problem David raised. The
> >>>> name is still synonymous with SR-IOV and it's defined on
> >>>> drivers/pci/iov.c, which is only built with CONFIG_PCI_IOV.
> >>>>
> >>>> - PCI_DEV_FLAGS_ASSIGNED should be unused after this series, why is it
> >>>> not removed?
> >>>
> >>> I guess it's still used, which is even worse because now we have
> >>> separate data elements, one tracking how many VFs are assigned from a PF
> >>> and another tracking each device that's assigned. What are we actually
> >>> gaining or fixing by doing this?
> >>
> >> Of course it is used to tracking PF/VF assigned, what we gained are - we hide the details
> >> In assignment helpers, we wouldn't bother the users anymore and implement what inside
> >> The helpers, my initial purpose is to simplify the ugly pci_vfs_assigned() with counter.
> >>
> >> I don't want to push more change in one step, that would out of control to get perfect result.
> >
> > But a counter means that we're tracking the data in two separate places,
> > which is generally a bad idea. Cleaning up direct access to flags is
> > fine, but creating a separate counter doesn't really seem to add any
> > value.
>
> If you are asked how many apples in your bag , you like to count them one by one and
> Give the answer ? What are you doing when you put them into the bag ?

If performance mattered, then yes, keeping a count may be advantageous.
Performance does not matter in any path where this is used.

> >>>>> drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c | 17 ++---------------
> >>>>> drivers/pci/iov.c | 20 ++++++++++++++++++++
> >>>>> drivers/xen/xen-pciback/pci_stub.c | 4 ++--
> >>>>> include/linux/pci.h | 4 ++++
> >>>>> virt/kvm/assigned-dev.c | 2 +-
> >>>>> virt/kvm/iommu.c | 4 ++--
> >>>>
> >>>> - This patch touch 4 separate logical code areas, who do you expect to
> >>>> ack and commit it? Split it up.
> >>>>
> >>>>> 6 files changed, 31 insertions(+), 20 deletions(-)
> >>>>>
> >>>>> diff --git a/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c b/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c
> >>>>> index 02c11a7..781040e 100644
> >>>>> --- a/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c
> >>>>> +++ b/drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c
> >>>>> @@ -693,22 +693,9 @@ complete_reset:
> >>>>> static bool i40e_vfs_are_assigned(struct i40e_pf *pf)
> >>>>> {
> >>>>> struct pci_dev *pdev = pf->pdev;
> >>>>> - struct pci_dev *vfdev;
> >>>>> -
> >>>>> - /* loop through all the VFs to see if we own any that are assigned */
> >>>>> - vfdev = pci_get_device(PCI_VENDOR_ID_INTEL, I40E_DEV_ID_VF , NULL);
> >>>>> - while (vfdev) {
> >>>>> - /* if we don't own it we don't care */
> >>>>> - if (vfdev->is_virtfn && pci_physfn(vfdev) == pdev) {
> >>>>> - /* if it is assigned we cannot release it */
> >>>>> - if (vfdev->dev_flags & PCI_DEV_FLAGS_ASSIGNED)
> >>>>> - return true;
> >>>>> - }
> >>>>>
> >>>>> - vfdev = pci_get_device(PCI_VENDOR_ID_INTEL,
> >>>>> - I40E_DEV_ID_VF,
> >>>>> - vfdev);
> >>>>> - }
> >>>>> + if (pci_vfs_assigned(pdev))
> >>>>> + return true;
> >>>>>
> >>>>> return false;
> >>>>> }
> >>>>> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> >>>>> index de7a747..090f827 100644
> >>>>> --- a/drivers/pci/iov.c
> >>>>> +++ b/drivers/pci/iov.c
> >>>>> @@ -644,6 +644,26 @@ int pci_vfs_assigned(struct pci_dev *dev)
> >>>>> EXPORT_SYMBOL_GPL(pci_vfs_assigned);
> >>>>>
> >>>>> /**
> >>>>> + * pci_iov_assign_device - assign device to VM
> >>>>> + * @pdev: the device to be assigned.
> >>>>> + */
> >>>>> +void pci_iov_assign_device(struct pci_dev *pdev)
> >>>>> +{
> >>>>> + pdev->dev_flags |= PCI_DEV_FLAGS_ASSIGNED;
> >>>>> +}
> >>>>> +EXPORT_SYMBOL_GPL(pci_iov_assign_device);
> >>>>> +
> >>>>> +/**
> >>>>> + * pci_iov_deassign_device - deasign device from VM
> >>>>> + * @pdev: the device to be deassigned.
> >>>>> + */
> >>>>> +void pci_iov_deassign_device(struct pci_dev *pdev)
> >>>>> +{
> >>>>> + pdev->dev_flags &= ~PCI_DEV_FLAGS_ASSIGNED;
> >>>>> +}
> >>>>> +EXPORT_SYMBOL_GPL(pci_iov_deassign_device);
> >>>>> +
> >>>>> +/**
> >>>>> * pci_sriov_set_totalvfs -- reduce the TotalVFs available
> >>>>> * @dev: the PCI PF device
> >>>>> * @numvfs: number that should be used for TotalVFs supported
> >>>>> diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c
> >>>>> index 62fcd48..27e00d1 100644
> >>>>> --- a/drivers/xen/xen-pciback/pci_stub.c
> >>>>> +++ b/drivers/xen/xen-pciback/pci_stub.c
> >>>>> @@ -133,7 +133,7 @@ static void pcistub_device_release(struct kref *kref)
> >>>>> xen_pcibk_config_free_dyn_fields(dev);
> >>>>> xen_pcibk_config_free_dev(dev);
> >>>>>
> >>>>> - dev->dev_flags &= ~PCI_DEV_FLAGS_ASSIGNED;
> >>>>> + pci_iov_deassign_device(dev);
> >>>>> pci_dev_put(dev);
> >>>>>
> >>>>> kfree(psdev);
> >>>>> @@ -404,7 +404,7 @@ static int pcistub_init_device(struct pci_dev *dev)
> >>>>> dev_dbg(&dev->dev, "reset device\n");
> >>>>> xen_pcibk_reset_device(dev);
> >>>>>
> >>>>> - dev->dev_flags |= PCI_DEV_FLAGS_ASSIGNED;
> >>>>> + pci_iov_assign_device(dev);
> >>>>> return 0;
> >>>>>
> >>>>> config_release:
> >>>>> diff --git a/include/linux/pci.h b/include/linux/pci.h
> >>>>> index aab57b4..5ece6d6 100644
> >>>>> --- a/include/linux/pci.h
> >>>>> +++ b/include/linux/pci.h
> >>>>> @@ -1603,6 +1603,8 @@ int pci_num_vf(struct pci_dev *dev);
> >>>>> int pci_vfs_assigned(struct pci_dev *dev);
> >>>>> int pci_sriov_set_totalvfs(struct pci_dev *dev, u16 numvfs);
> >>>>> int pci_sriov_get_totalvfs(struct pci_dev *dev);
> >>>>> +void pci_iov_assign_device(struct pci_dev *dev);
> >>>>> +void pci_iov_deassign_device(struct pci_dev *dev);
> >>>>> #else
> >>>>> static inline int pci_enable_sriov(struct pci_dev *dev, int nr_virtfn)
> >>>>> { return -ENODEV; }
> >>>>> @@ -1614,6 +1616,8 @@ static inline int pci_sriov_set_totalvfs(struct pci_dev *dev, u16 numvfs)
> >>>>> { return 0; }
> >>>>> static inline int pci_sriov_get_totalvfs(struct pci_dev *dev)
> >>>>> { return 0; }
> >>>>> +static inline void pci_iov_assign_device(struct pci_dev *dev) { }
> >>>>> +static inline void pci_iov_deassign_device(struct pci_dev *dev) { }
> >>>>> #endif
> >>>>>
> >>>>> #if defined(CONFIG_HOTPLUG_PCI) || defined(CONFIG_HOTPLUG_PCI_MODULE)
> >>>>> diff --git a/virt/kvm/assigned-dev.c b/virt/kvm/assigned-dev.c
> >>>>> index bf06577..7fac58d 100644
> >>>>> --- a/virt/kvm/assigned-dev.c
> >>>>> +++ b/virt/kvm/assigned-dev.c
> >>>>> @@ -302,7 +302,7 @@ static void kvm_free_assigned_device(struct kvm *kvm,
> >>>>> else
> >>>>> pci_restore_state(assigned_dev->dev);
> >>>>>
> >>>>> - assigned_dev->dev->dev_flags &= ~PCI_DEV_FLAGS_ASSIGNED;
> >>>>> + pci_iov_deassign_device(assigned_dev->dev);
> >>>>>
> >>>>> pci_release_regions(assigned_dev->dev);
> >>>>> pci_disable_device(assigned_dev->dev);
> >>>>> diff --git a/virt/kvm/iommu.c b/virt/kvm/iommu.c
> >>>>> index 0df7d4b..641ee73 100644
> >>>>> --- a/virt/kvm/iommu.c
> >>>>> +++ b/virt/kvm/iommu.c
> >>>>> @@ -194,7 +194,7 @@ int kvm_assign_device(struct kvm *kvm,
> >>>>> goto out_unmap;
> >>>>> }
> >>>>>
> >>>>> - pdev->dev_flags |= PCI_DEV_FLAGS_ASSIGNED;
> >>>>> + pci_iov_assign_device(pdev);
> >>>>>
> >>>>> dev_info(&pdev->dev, "kvm assign device\n");
> >>>>>
> >>>>> @@ -220,7 +220,7 @@ int kvm_deassign_device(struct kvm *kvm,
> >>>>>
> >>>>> iommu_detach_device(domain, &pdev->dev);
> >>>>>
> >>>>> - pdev->dev_flags &= ~PCI_DEV_FLAGS_ASSIGNED;
> >>>>> + pci_iov_deassign_device(pdev);
> >>>>>
> >>>>> dev_info(&pdev->dev, "kvm deassign device\n");
> >
> >
> >