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Date: Thu, 10 Jul 2014 20:33:57 -0600
From: Alex Williamson <alex.williamson@...hat.com>
To: ethan zhao <ethan.zhao@...cle.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 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.
> >>> 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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