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SubjectRe: [PATCH 1/4] PCI: introduce VFs reference counter and simplify pci_vfs_assigned() implementation
Alex,
Thanks for your reviewing, when I create the patch order, I thought
about the question you concerned for
quit a while, make every patch be independent to each other as possible
as I could, so we can do bisect when hit
problem.

I manage to take more time to figure out better patch order.

Thanks,
Ethan

On 2014/7/11 9:48, Alex Williamson wrote:
> 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
i40e only could be fixed with new interface, so it couldn't
be the first one.
> patch 2 - create assign/deassign that uses dev_flags
This will be the first ?
> patch 3 - convert users to new interface
Have to be the later step.
> patch 4 - convert interface to use atomic_t
Could it be standalone step ?

Let me think about it.

> 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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