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Date: Fri, 11 Jul 2014 10:29:12 +0800
From: ethan zhao <ethan.zhao@...cle.com>
To: Alex Williamson <alex.williamson@...hat.com>
CC: bhelgaas@...gle.com, konrad.wilk@...cle.com,
boris.ostrovsky@...cle.com, david.vrabel@...rix.com,
gleb@...nel.org, pbonzini@...hat.com, jeffrey.t.kirsher@...el.com,
jesse.brandeburg@...el.com, bruce.w.allan@...el.com,
carolyn.wyborny@...el.com, donald.c.skidmore@...el.com,
gregory.v.rose@...el.com, alexander.h.duyck@...el.com,
john.ronciak@...el.com, mitch.a.williams@...el.com,
linux-pci@...r.kernel.org, kvm@...r.kernel.org,
linux.nics@...el.com, e1000-devel@...ts.sourceforge.net,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
ethan.kernel@...il.com, vaughan.cao@...cle.com
Subject: Re: [PATCH 1/4] PCI: introduce VFs reference counter and simplify
pci_vfs_assigned() implementation
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.
Thanks,
Ethan
>
>>> 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@...cle.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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