PCI: Lock each enable/disable num_vfs operation in sysfs

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.

Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
CC: Alexander Duyck <alexander.h.duyck@intel.com>

3 files changed, 17 insertions, 15 deletions

diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index 47227820406d..2479ae876482 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 @@ failed2:
         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 066628776e1b..25d010d449a3 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;
         }
 
         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 cb17db242f30..8dd38e69d6f2 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 */
 };