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Date: Thu, 10 Jul 2014 20:22:04 -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 10:10 +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?
> > 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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