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SubjectRe: [PATCH 1/4] PCI: introduce VFs reference counter and simplify pci_vfs_assigned() implementation
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Since there's no 0th patch, I guess I'll comment here. This series is
not bisectable, patch 1 breaks the existing implementation. I'd
suggest:

patch 1 - fix i40e
patch 2 - create assign/deassign that uses dev_flags
patch 3 - convert users to new interface
patch 4 - convert interface to use atomic_t

IMHO, the assigned flag is a horrible hack and I don't know why drivers
like xenback need to use it. KVM needs to use it because it doesn't
actually have a driver to bind to when a device is assigned, it's happy
to assign devices without any driver. Thanks,

Alex


On Fri, 2014-07-11 at 08:47 +0800, Ethan Zhao wrote:
> Current implementation of helper function pci_vfs_assigned() is a little complex, to
> get sum of VFs that assigned to VM, access low level configuration space register and
> then loop in traversing device tree.
>
> This patch introduce an atomic reference counter for VFs that assigned to VM in struct
> pci_sriov, and compose two more helper functions
>
> pci_sriov_assign_device(),
> pci_sriov_deassign_device()
>
> to replace manipulation to device flag and the meanwhile increase and decease the counter.
>
> Passed building on 3.15.5
>
> Signed-off-by: Ethan Zhao <ethan.zhao@oracle.com>
> ---
> drivers/pci/iov.c | 65 ++++++++++++++++++++++++++++----------------------
> drivers/pci/pci.h | 1 +
> include/linux/pci.h | 4 +++
> 3 files changed, 41 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index de7a747..72e267f 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -382,6 +382,7 @@ found:
> iov->nres = nres;
> iov->ctrl = ctrl;
> iov->total_VFs = total;
> + atomic_set(&iov->VFs_assigned_cnt, 0);
> iov->offset = offset;
> iov->stride = stride;
> iov->pgsz = pgsz;
> @@ -603,45 +604,51 @@ int pci_num_vf(struct pci_dev *dev)
> EXPORT_SYMBOL_GPL(pci_num_vf);
>
> /**
> - * pci_vfs_assigned - returns number of VFs are assigned to a guest
> - * @dev: the PCI device
> + * pci_vfs_assigned - returns number of VFs are assigned to VM
> + * @dev: the physical PCI device that contains the VFs.
> *
> - * Returns number of VFs belonging to this device that are assigned to a guest.
> + * Returns number of VFs belonging to this device that are assigned to VM.
> * If device is not a physical function returns 0.
> */
> int pci_vfs_assigned(struct pci_dev *dev)
> {
> - struct pci_dev *vfdev;
> - unsigned int vfs_assigned = 0;
> - unsigned short dev_id;
> -
> - /* only search if we are a PF */
> if (!dev->is_physfn)
> return 0;
> + if (dev->sriov)
> + return atomic_read(&dev->sriov->VFs_assigned_cnt);
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(pci_vfs_assigned);
>
> - /*
> - * determine the device ID for the VFs, the vendor ID will be the
> - * same as the PF so there is no need to check for that one
> - */
> - pci_read_config_word(dev, dev->sriov->pos + PCI_SRIOV_VF_DID, &dev_id);
> -
> - /* loop through all the VFs to see if we own any that are assigned */
> - vfdev = pci_get_device(dev->vendor, dev_id, NULL);
> - while (vfdev) {
> - /*
> - * It is considered assigned if it is a virtual function with
> - * our dev as the physical function and the assigned bit is set
> - */
> - if (vfdev->is_virtfn && (vfdev->physfn == dev) &&
> - (vfdev->dev_flags & PCI_DEV_FLAGS_ASSIGNED))
> - vfs_assigned++;
> -
> - vfdev = pci_get_device(dev->vendor, dev_id, vfdev);
> - }
> +/**
> + * pci_sriov_assign_device - assign device to VM
> + * @pdev: the device to be assigned.
> + */
> +void pci_sriov_assign_device(struct pci_dev *pdev)
> +{
> + pdev->dev_flags |= PCI_DEV_FLAGS_ASSIGNED;
> + if (pdev->is_virtfn && !pdev->is_physfn)
> + if (pdev->physfn)
> + if (pdev->physfn->sriov)
> + atomic_inc(&pdev->physfn->sriov->
> + VFs_assigned_cnt);
> +}
> +EXPORT_SYMBOL_GPL(pci_sriov_assign_device);
>
> - return vfs_assigned;
> +/**
> + * pci_sriov_deassign_device - deasign device from VM
> + * @pdev: the device to be deassigned.
> + */
> +void pci_sriov_deassign_device(struct pci_dev *pdev)
> +{
> + pdev->dev_flags &= ~PCI_DEV_FLAGS_ASSIGNED;
> + if (pdev->is_virtfn && !pdev->is_physfn)
> + if (pdev->physfn)
> + if (pdev->physfn->sriov)
> + atomic_dec(&pdev->physfn->sriov->
> + VFs_assigned_cnt);
> }
> -EXPORT_SYMBOL_GPL(pci_vfs_assigned);
> +EXPORT_SYMBOL_GPL(pci_sriov_deassign_device);
>
> /**
> * pci_sriov_set_totalvfs -- reduce the TotalVFs available
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 6bd0822..d17bda2 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -235,6 +235,7 @@ struct pci_sriov {
> u32 pgsz; /* page size for BAR alignment */
> u8 link; /* Function Dependency Link */
> u16 driver_max_VFs; /* max num VFs driver supports */
> + atomic_t VFs_assigned_cnt; /* counter of VFs assigned to VM */
> struct pci_dev *dev; /* lowest numbered PF */
> struct pci_dev *self; /* this PF */
> struct mutex lock; /* lock for VF bus */
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index aab57b4..5cf6833 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1601,6 +1601,8 @@ int pci_enable_sriov(struct pci_dev *dev, int nr_virtfn);
> void pci_disable_sriov(struct pci_dev *dev);
> int pci_num_vf(struct pci_dev *dev);
> int pci_vfs_assigned(struct pci_dev *dev);
> +void pci_sriov_assign_device(struct pci_dev *dev);
> +void pci_sriov_deassign_device(struct pci_dev *dev);
> int pci_sriov_set_totalvfs(struct pci_dev *dev, u16 numvfs);
> int pci_sriov_get_totalvfs(struct pci_dev *dev);
> #else
> @@ -1610,6 +1612,8 @@ static inline void pci_disable_sriov(struct pci_dev *dev) { }
> static inline int pci_num_vf(struct pci_dev *dev) { return 0; }
> static inline int pci_vfs_assigned(struct pci_dev *dev)
> { return 0; }
> +static inline void pci_sriov_assign_device(struct pci_dev *dev) { }
> +static inline void pci_sriov_deassign_device(struct pci_dev *dev) { }
> 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)





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