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Message-ID: <1483744662.3868.1.camel@gmail.com>
Date: Fri, 06 Jan 2017 15:17:42 -0800
From: Greg <gvrose8192@...il.com>
To: Emil Tantilov <emil.s.tantilov@...el.com>
Cc: linux-pci@...r.kernel.org, intel-wired-lan@...ts.osuosl.org,
alexander.h.duyck@...el.com, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] PCI: lock each enable/disable num_vfs operation in
sysfs
On Fri, 2017-01-06 at 13:59 -0800, Emil Tantilov wrote:
> Enabling/disabling SRIOV via sysfs by echo-ing multiple values
> simultaneously:
>
> echo 63 > /sys/class/net/ethX/device/sriov_numvfs&
> echo 63 > /sys/class/net/ethX/device/sriov_numvfs
>
> sleep 5
>
> echo 0 > /sys/class/net/ethX/device/sriov_numvfs&
> echo 0 > /sys/class/net/ethX/device/sriov_numvfs
>
> Results in the following bug:
>
> kernel BUG at drivers/pci/iov.c:495!
> invalid opcode: 0000 [#1] SMP
> CPU: 1 PID: 8050 Comm: bash Tainted: G W 4.9.0-rc7-net-next #2092
> RIP: 0010:[<ffffffff813b1647>]
> [<ffffffff813b1647>] pci_iov_release+0x57/0x60
>
> Call Trace:
> [<ffffffff81391726>] pci_release_dev+0x26/0x70
> [<ffffffff8155be6e>] device_release+0x3e/0xb0
> [<ffffffff81365ee7>] kobject_cleanup+0x67/0x180
> [<ffffffff81365d9d>] kobject_put+0x2d/0x60
> [<ffffffff8155bc27>] put_device+0x17/0x20
> [<ffffffff8139c08a>] pci_dev_put+0x1a/0x20
> [<ffffffff8139cb6b>] pci_get_dev_by_id+0x5b/0x90
> [<ffffffff8139cca5>] pci_get_subsys+0x35/0x40
> [<ffffffff8139ccc8>] pci_get_device+0x18/0x20
> [<ffffffff8139ccfb>] pci_get_domain_bus_and_slot+0x2b/0x60
> [<ffffffff813b09e7>] pci_iov_remove_virtfn+0x57/0x180
> [<ffffffff813b0b95>] pci_disable_sriov+0x65/0x140
> [<ffffffffa00a1af7>] ixgbe_disable_sriov+0xc7/0x1d0 [ixgbe]
> [<ffffffffa00a1e9d>] ixgbe_pci_sriov_configure+0x3d/0x170 [ixgbe]
> [<ffffffff8139d28c>] sriov_numvfs_store+0xdc/0x130
> ...
> RIP [<ffffffff813b1647>] pci_iov_release+0x57/0x60
>
> Use the existing mutex lock to protect each enable/disable operation.
>
> -v2: move the existing lock from protecting the config of the IOV bus
> to protecting the writes to sriov_numvfs in sysfs without maintaining
> a "locked" version of pci_iov_add/remove_virtfn().
> As suggested by Gavin Shan <gwshan@...ux.vnet.ibm.com>
>
> CC: Alexander Duyck <alexander.h.duyck@...el.com>
> Signed-off-by: Emil Tantilov <emil.s.tantilov@...el.com>
> ---
> drivers/pci/iov.c | 7 -------
> drivers/pci/pci-sysfs.c | 23 ++++++++++++++++-------
> drivers/pci/pci.h | 2 +-
> 3 files changed, 17 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index 4722782..2479ae8 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -124,7 +124,6 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id, int reset)
> struct pci_sriov *iov = dev->sriov;
> struct pci_bus *bus;
>
> - mutex_lock(&iov->dev->sriov->lock);
> bus = virtfn_add_bus(dev->bus, pci_iov_virtfn_bus(dev, id));
> if (!bus)
> goto failed;
> @@ -162,7 +161,6 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id, int reset)
> __pci_reset_function(virtfn);
>
> pci_device_add(virtfn, virtfn->bus);
> - mutex_unlock(&iov->dev->sriov->lock);
>
> pci_bus_add_device(virtfn);
> sprintf(buf, "virtfn%u", id);
> @@ -181,12 +179,10 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id, int reset)
> sysfs_remove_link(&dev->dev.kobj, buf);
> failed1:
> pci_dev_put(dev);
> - mutex_lock(&iov->dev->sriov->lock);
> pci_stop_and_remove_bus_device(virtfn);
> failed0:
> virtfn_remove_bus(dev->bus, bus);
> failed:
> - mutex_unlock(&iov->dev->sriov->lock);
>
> return rc;
> }
> @@ -195,7 +191,6 @@ void pci_iov_remove_virtfn(struct pci_dev *dev, int id, int reset)
> {
> char buf[VIRTFN_ID_LEN];
> struct pci_dev *virtfn;
> - struct pci_sriov *iov = dev->sriov;
>
> virtfn = pci_get_domain_bus_and_slot(pci_domain_nr(dev->bus),
> pci_iov_virtfn_bus(dev, id),
> @@ -218,10 +213,8 @@ void pci_iov_remove_virtfn(struct pci_dev *dev, int id, int reset)
> if (virtfn->dev.kobj.sd)
> sysfs_remove_link(&virtfn->dev.kobj, "physfn");
>
> - mutex_lock(&iov->dev->sriov->lock);
> pci_stop_and_remove_bus_device(virtfn);
> virtfn_remove_bus(dev->bus, virtfn->bus);
> - mutex_unlock(&iov->dev->sriov->lock);
>
> /* balance pci_get_domain_bus_and_slot() */
> pci_dev_put(virtfn);
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index 0666287..25d010d 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -472,6 +472,7 @@ static ssize_t sriov_numvfs_store(struct device *dev,
> const char *buf, size_t count)
> {
> struct pci_dev *pdev = to_pci_dev(dev);
> + struct pci_sriov *iov = pdev->sriov;
> int ret;
> u16 num_vfs;
>
> @@ -482,38 +483,46 @@ static ssize_t sriov_numvfs_store(struct device *dev,
> if (num_vfs > pci_sriov_get_totalvfs(pdev))
> return -ERANGE;
>
> + mutex_lock(&iov->dev->sriov->lock);
> +
> if (num_vfs == pdev->sriov->num_VFs)
> - return count; /* no change */
> + goto exit;
>
> /* is PF driver loaded w/callback */
> if (!pdev->driver || !pdev->driver->sriov_configure) {
> dev_info(&pdev->dev, "Driver doesn't support SRIOV configuration via sysfs\n");
> - return -ENOSYS;
> + ret = -ENOENT;
> + goto exit;
Hi Emil,
Generally the patch looks fine to me - but I am wondering why the change
from -ENOSYS TO -ENOENT?
Thanks,
- Greg
> }
>
> if (num_vfs == 0) {
> /* disable VFs */
> ret = pdev->driver->sriov_configure(pdev, 0);
> - if (ret < 0)
> - return ret;
> - return count;
> + goto exit;
> }
>
> /* enable VFs */
> if (pdev->sriov->num_VFs) {
> dev_warn(&pdev->dev, "%d VFs already enabled. Disable before enabling %d VFs\n",
> pdev->sriov->num_VFs, num_vfs);
> - return -EBUSY;
> + ret = -EBUSY;
> + goto exit;
> }
>
> ret = pdev->driver->sriov_configure(pdev, num_vfs);
> if (ret < 0)
> - return ret;
> + goto exit;
>
> if (ret != num_vfs)
> dev_warn(&pdev->dev, "%d VFs requested; only %d enabled\n",
> num_vfs, ret);
>
> +exit:
> + mutex_unlock(&iov->dev->sriov->lock);
> +
> + if (ret < 0)
> + return ret;
> +
> return count;
> }
>
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index cb17db2..8dd38e6 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -270,7 +270,7 @@ struct pci_sriov {
> u16 driver_max_VFs; /* max num VFs driver supports */
> struct pci_dev *dev; /* lowest numbered PF */
> struct pci_dev *self; /* this PF */
> - struct mutex lock; /* lock for VF bus */
> + struct mutex lock; /* lock for setting sriov_numvfs in sysfs */
> resource_size_t barsz[PCI_SRIOV_NUM_BARS]; /* VF BAR size */
> };
>
>
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