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SubjectRe: [PATCH 1/4] PCI: introduce VFs reference counter and simplify pci_vfs_assigned() implementation

On 2014/7/11 10:33, Alex Williamson wrote:
> On Fri, 2014-07-11 at 10:29 +0800, ethan zhao wrote:
>> On 2014/7/11 10:22, Alex Williamson wrote:
>>> On Fri, 2014-07-11 at 10:10 +0800, ethan zhao wrote:
>>>> 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.
>>> It looks like i40e just has it's own copy of pci_vfs_assigned(), why
>>> can't your current patch 4/4 be applied now?
>> Yes, i40e has its local copy of pci_vfs_assigned(),it could be
>> simplified .
>> with new interface,in another word, its a user of new interface.
> It's a user of the existing interface. You're missing the point,
> abstract all the users of the assigned dev_flags first, then you're free
> to fix the implementation of the interface in one shot without breaking
> anything.
Great,you hit the center this time, agree !
>>>>> 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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