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

[Alex Williamson <alex.williamson@redhat.com>]

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.

> >>> 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");
> > 
> > 
> > 




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