Patchwork [RFC,v1,01/22] PCI: use pci_get_domain_bus_and_slot() to avoid race conditions

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Submitter Jiang Liu
Date Aug. 7, 2012, 4:10 p.m.
Message ID <1344355862-2726-2-git-send-email-jiang.liu@huawei.com>
Download mbox | patch
Permalink /patch/175725/
State Not Applicable
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Comments

Jiang Liu - Aug. 7, 2012, 4:10 p.m.
There's a typical usage pattern to search a PCI device under a specific
PCI bus (domian, busno) as below:
struct pci_bus *pci_bus = pci_find_bus(domain, busno);
struct pci_dev *pci_dev = pci_get_slot(pci_bus, devfn);

The above code has a race window between pci_find_bus() and pci_get_slot()
if PCI hotplug operations happen between them which removes the pci_bus.
So use PCI hotplug safe interface pci_get_domain_bus_and_slot() instead,
which also reduces code complexity.

Signed-off-by: Jiang Liu <liuj97@gmail.com>
---
 arch/ia64/sn/kernel/io_common.c      |    4 +---
 drivers/gpu/vga/vgaarb.c             |   15 +++------------
 drivers/pci/hotplug/cpcihp_generic.c |    8 ++------
 drivers/pci/iov.c                    |    8 ++------
 drivers/pci/xen-pcifront.c           |   10 ++--------
 5 files changed, 10 insertions(+), 35 deletions(-)
Bjorn Helgaas - Sept. 11, 2012, 10 p.m.
On Tue, Aug 7, 2012 at 10:10 AM, Jiang Liu <liuj97@gmail.com> wrote:
> There's a typical usage pattern to search a PCI device under a specific
> PCI bus (domian, busno) as below:
> struct pci_bus *pci_bus = pci_find_bus(domain, busno);
> struct pci_dev *pci_dev = pci_get_slot(pci_bus, devfn);
>
> The above code has a race window between pci_find_bus() and pci_get_slot()
> if PCI hotplug operations happen between them which removes the pci_bus.
> So use PCI hotplug safe interface pci_get_domain_bus_and_slot() instead,
> which also reduces code complexity.

This makes sense to me.  If we support hotplug, it's fundamentally
unsafe to keep a struct pci_bus * without having a reference or some
way to make sure it doesn't go away.  I think we should try to
eradicate all uses of pci_find_bus() and pci_find_next_bus().

> Signed-off-by: Jiang Liu <liuj97@gmail.com>
> ---
>  arch/ia64/sn/kernel/io_common.c      |    4 +---
>  drivers/gpu/vga/vgaarb.c             |   15 +++------------
>  drivers/pci/hotplug/cpcihp_generic.c |    8 ++------
>  drivers/pci/iov.c                    |    8 ++------
>  drivers/pci/xen-pcifront.c           |   10 ++--------
>  5 files changed, 10 insertions(+), 35 deletions(-)
>
> diff --git a/arch/ia64/sn/kernel/io_common.c b/arch/ia64/sn/kernel/io_common.c
> index fbb5f2f..8630875 100644
> --- a/arch/ia64/sn/kernel/io_common.c
> +++ b/arch/ia64/sn/kernel/io_common.c
> @@ -229,7 +229,6 @@ void sn_pci_fixup_slot(struct pci_dev *dev, struct pcidev_info *pcidev_info,
>  {
>         int segment = pci_domain_nr(dev->bus);
>         struct pcibus_bussoft *bs;
> -       struct pci_bus *host_pci_bus;
>         struct pci_dev *host_pci_dev;
>         unsigned int bus_no, devfn;
>
> @@ -245,8 +244,7 @@ void sn_pci_fixup_slot(struct pci_dev *dev, struct pcidev_info *pcidev_info,
>
>         bus_no = (pcidev_info->pdi_slot_host_handle >> 32) & 0xff;
>         devfn = pcidev_info->pdi_slot_host_handle & 0xffffffff;
> -       host_pci_bus = pci_find_bus(segment, bus_no);
> -       host_pci_dev = pci_get_slot(host_pci_bus, devfn);
> +       host_pci_dev = pci_get_domain_bus_and_slot(segment, bus_no, devfn);
>
>         pcidev_info->host_pci_dev = host_pci_dev;
>         pcidev_info->pdi_linux_pcidev = dev;
> diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c
> index 3df8fc0..b6852b7 100644
> --- a/drivers/gpu/vga/vgaarb.c
> +++ b/drivers/gpu/vga/vgaarb.c
> @@ -1066,7 +1066,6 @@ static ssize_t vga_arb_write(struct file *file, const char __user * buf,
>                 }
>
>         } else if (strncmp(curr_pos, "target ", 7) == 0) {
> -               struct pci_bus *pbus;
>                 unsigned int domain, bus, devfn;
>                 struct vga_device *vgadev;
>
> @@ -1085,19 +1084,11 @@ static ssize_t vga_arb_write(struct file *file, const char __user * buf,
>                         pr_debug("vgaarb: %s ==> %x:%x:%x.%x\n", curr_pos,
>                                 domain, bus, PCI_SLOT(devfn), PCI_FUNC(devfn));
>
> -                       pbus = pci_find_bus(domain, bus);
> -                       pr_debug("vgaarb: pbus %p\n", pbus);
> -                       if (pbus == NULL) {
> -                               pr_err("vgaarb: invalid PCI domain and/or bus address %x:%x\n",
> -                                       domain, bus);
> -                               ret_val = -ENODEV;
> -                               goto done;
> -                       }
> -                       pdev = pci_get_slot(pbus, devfn);
> +                       pdev = pci_get_domain_bus_and_slot(domain, bus, devfn);
>                         pr_debug("vgaarb: pdev %p\n", pdev);
>                         if (!pdev) {
> -                               pr_err("vgaarb: invalid PCI address %x:%x\n",
> -                                       bus, devfn);
> +                               pr_err("vgaarb: invalid PCI address %x:%x:%x\n",
> +                                       domain, bus, devfn);
>                                 ret_val = -ENODEV;
>                                 goto done;
>                         }
> diff --git a/drivers/pci/hotplug/cpcihp_generic.c b/drivers/pci/hotplug/cpcihp_generic.c
> index 81af764..a6a71c4 100644
> --- a/drivers/pci/hotplug/cpcihp_generic.c
> +++ b/drivers/pci/hotplug/cpcihp_generic.c
> @@ -154,12 +154,8 @@ static int __init cpcihp_generic_init(void)
>         if(!r)
>                 return -EBUSY;
>
> -       bus = pci_find_bus(0, bridge_busnr);
> -       if (!bus) {
> -               err("Invalid bus number %d", bridge_busnr);
> -               return -EINVAL;
> -       }
> -       dev = pci_get_slot(bus, PCI_DEVFN(bridge_slot, 0));
> +       dev = pci_get_domain_bus_and_slot(0, bridge_busnr,
> +                                         PCI_DEVFN(bridge_slot, 0));
>         if(!dev || dev->hdr_type != PCI_HEADER_TYPE_BRIDGE) {
>                 err("Invalid bridge device %s", bridge);
>                 pci_dev_put(dev);
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index 74bbaf8..c7d2969 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -152,15 +152,11 @@ failed1:
>  static void virtfn_remove(struct pci_dev *dev, int id, int reset)
>  {
>         char buf[VIRTFN_ID_LEN];
> -       struct pci_bus *bus;
>         struct pci_dev *virtfn;
>         struct pci_sriov *iov = dev->sriov;
>
> -       bus = pci_find_bus(pci_domain_nr(dev->bus), virtfn_bus(dev, id));
> -       if (!bus)
> -               return;
> -
> -       virtfn = pci_get_slot(bus, virtfn_devfn(dev, id));
> +       virtfn = pci_get_domain_bus_and_slot(pci_domain_nr(dev->bus),
> +                       virtfn_bus(dev, id), virtfn_devfn(dev, id));
>         if (!virtfn)
>                 return;
>
> diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
> index d6cc62c..def8d0b 100644
> --- a/drivers/pci/xen-pcifront.c
> +++ b/drivers/pci/xen-pcifront.c
> @@ -982,7 +982,6 @@ static int pcifront_detach_devices(struct pcifront_device *pdev)
>         int err = 0;
>         int i, num_devs;
>         unsigned int domain, bus, slot, func;
> -       struct pci_bus *pci_bus;
>         struct pci_dev *pci_dev;
>         char str[64];
>
> @@ -1032,13 +1031,8 @@ static int pcifront_detach_devices(struct pcifront_device *pdev)
>                         goto out;
>                 }
>
> -               pci_bus = pci_find_bus(domain, bus);
> -               if (!pci_bus) {
> -                       dev_dbg(&pdev->xdev->dev, "Cannot get bus %04x:%02x\n",
> -                               domain, bus);
> -                       continue;
> -               }
> -               pci_dev = pci_get_slot(pci_bus, PCI_DEVFN(slot, func));
> +               pci_dev = pci_get_domain_bus_and_slot(domain, bus,
> +                               PCI_DEVFN(slot, func));
>                 if (!pci_dev) {
>                         dev_dbg(&pdev->xdev->dev,
>                                 "Cannot get PCI device %04x:%02x:%02x.%d\n",
> --
> 1.7.9.5
>
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Jiang Liu - Sept. 12, 2012, 8:37 a.m.
On 2012-9-12 6:00, Bjorn Helgaas wrote:
> On Tue, Aug 7, 2012 at 10:10 AM, Jiang Liu <liuj97@gmail.com> wrote:
>> There's a typical usage pattern to search a PCI device under a specific
>> PCI bus (domian, busno) as below:
>> struct pci_bus *pci_bus = pci_find_bus(domain, busno);
>> struct pci_dev *pci_dev = pci_get_slot(pci_bus, devfn);
>>
>> The above code has a race window between pci_find_bus() and pci_get_slot()
>> if PCI hotplug operations happen between them which removes the pci_bus.
>> So use PCI hotplug safe interface pci_get_domain_bus_and_slot() instead,
>> which also reduces code complexity.
> 
> This makes sense to me.  If we support hotplug, it's fundamentally
> unsafe to keep a struct pci_bus * without having a reference or some
> way to make sure it doesn't go away.  I think we should try to
> eradicate all uses of pci_find_bus() and pci_find_next_bus().
Hi Bjorn
	I have split out these into a separate patch set at
http://www.spinics.net/lists/linux-pci/msg17227.html.
	In my latest PCI bus lock patch set, I have introduced a new
interface pci_get_bus() to replace pci_find_bus(). But pci_find_next_bus()
is a little harder to deal with, still need more work here.
	Thanks!

> 
>> Signed-off-by: Jiang Liu <liuj97@gmail.com>
>> ---
>>  arch/ia64/sn/kernel/io_common.c      |    4 +---
>>  drivers/gpu/vga/vgaarb.c             |   15 +++------------
>>  drivers/pci/hotplug/cpcihp_generic.c |    8 ++------
>>  drivers/pci/iov.c                    |    8 ++------
>>  drivers/pci/xen-pcifront.c           |   10 ++--------
>>  5 files changed, 10 insertions(+), 35 deletions(-)
>>
>> diff --git a/arch/ia64/sn/kernel/io_common.c b/arch/ia64/sn/kernel/io_common.c
>> index fbb5f2f..8630875 100644
>> --- a/arch/ia64/sn/kernel/io_common.c
>> +++ b/arch/ia64/sn/kernel/io_common.c
>> @@ -229,7 +229,6 @@ void sn_pci_fixup_slot(struct pci_dev *dev, struct pcidev_info *pcidev_info,
>>  {
>>         int segment = pci_domain_nr(dev->bus);
>>         struct pcibus_bussoft *bs;
>> -       struct pci_bus *host_pci_bus;
>>         struct pci_dev *host_pci_dev;
>>         unsigned int bus_no, devfn;
>>
>> @@ -245,8 +244,7 @@ void sn_pci_fixup_slot(struct pci_dev *dev, struct pcidev_info *pcidev_info,
>>
>>         bus_no = (pcidev_info->pdi_slot_host_handle >> 32) & 0xff;
>>         devfn = pcidev_info->pdi_slot_host_handle & 0xffffffff;
>> -       host_pci_bus = pci_find_bus(segment, bus_no);
>> -       host_pci_dev = pci_get_slot(host_pci_bus, devfn);
>> +       host_pci_dev = pci_get_domain_bus_and_slot(segment, bus_no, devfn);
>>
>>         pcidev_info->host_pci_dev = host_pci_dev;
>>         pcidev_info->pdi_linux_pcidev = dev;
>> diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c
>> index 3df8fc0..b6852b7 100644
>> --- a/drivers/gpu/vga/vgaarb.c
>> +++ b/drivers/gpu/vga/vgaarb.c
>> @@ -1066,7 +1066,6 @@ static ssize_t vga_arb_write(struct file *file, const char __user * buf,
>>                 }
>>
>>         } else if (strncmp(curr_pos, "target ", 7) == 0) {
>> -               struct pci_bus *pbus;
>>                 unsigned int domain, bus, devfn;
>>                 struct vga_device *vgadev;
>>
>> @@ -1085,19 +1084,11 @@ static ssize_t vga_arb_write(struct file *file, const char __user * buf,
>>                         pr_debug("vgaarb: %s ==> %x:%x:%x.%x\n", curr_pos,
>>                                 domain, bus, PCI_SLOT(devfn), PCI_FUNC(devfn));
>>
>> -                       pbus = pci_find_bus(domain, bus);
>> -                       pr_debug("vgaarb: pbus %p\n", pbus);
>> -                       if (pbus == NULL) {
>> -                               pr_err("vgaarb: invalid PCI domain and/or bus address %x:%x\n",
>> -                                       domain, bus);
>> -                               ret_val = -ENODEV;
>> -                               goto done;
>> -                       }
>> -                       pdev = pci_get_slot(pbus, devfn);
>> +                       pdev = pci_get_domain_bus_and_slot(domain, bus, devfn);
>>                         pr_debug("vgaarb: pdev %p\n", pdev);
>>                         if (!pdev) {
>> -                               pr_err("vgaarb: invalid PCI address %x:%x\n",
>> -                                       bus, devfn);
>> +                               pr_err("vgaarb: invalid PCI address %x:%x:%x\n",
>> +                                       domain, bus, devfn);
>>                                 ret_val = -ENODEV;
>>                                 goto done;
>>                         }
>> diff --git a/drivers/pci/hotplug/cpcihp_generic.c b/drivers/pci/hotplug/cpcihp_generic.c
>> index 81af764..a6a71c4 100644
>> --- a/drivers/pci/hotplug/cpcihp_generic.c
>> +++ b/drivers/pci/hotplug/cpcihp_generic.c
>> @@ -154,12 +154,8 @@ static int __init cpcihp_generic_init(void)
>>         if(!r)
>>                 return -EBUSY;
>>
>> -       bus = pci_find_bus(0, bridge_busnr);
>> -       if (!bus) {
>> -               err("Invalid bus number %d", bridge_busnr);
>> -               return -EINVAL;
>> -       }
>> -       dev = pci_get_slot(bus, PCI_DEVFN(bridge_slot, 0));
>> +       dev = pci_get_domain_bus_and_slot(0, bridge_busnr,
>> +                                         PCI_DEVFN(bridge_slot, 0));
>>         if(!dev || dev->hdr_type != PCI_HEADER_TYPE_BRIDGE) {
>>                 err("Invalid bridge device %s", bridge);
>>                 pci_dev_put(dev);
>> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
>> index 74bbaf8..c7d2969 100644
>> --- a/drivers/pci/iov.c
>> +++ b/drivers/pci/iov.c
>> @@ -152,15 +152,11 @@ failed1:
>>  static void virtfn_remove(struct pci_dev *dev, int id, int reset)
>>  {
>>         char buf[VIRTFN_ID_LEN];
>> -       struct pci_bus *bus;
>>         struct pci_dev *virtfn;
>>         struct pci_sriov *iov = dev->sriov;
>>
>> -       bus = pci_find_bus(pci_domain_nr(dev->bus), virtfn_bus(dev, id));
>> -       if (!bus)
>> -               return;
>> -
>> -       virtfn = pci_get_slot(bus, virtfn_devfn(dev, id));
>> +       virtfn = pci_get_domain_bus_and_slot(pci_domain_nr(dev->bus),
>> +                       virtfn_bus(dev, id), virtfn_devfn(dev, id));
>>         if (!virtfn)
>>                 return;
>>
>> diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
>> index d6cc62c..def8d0b 100644
>> --- a/drivers/pci/xen-pcifront.c
>> +++ b/drivers/pci/xen-pcifront.c
>> @@ -982,7 +982,6 @@ static int pcifront_detach_devices(struct pcifront_device *pdev)
>>         int err = 0;
>>         int i, num_devs;
>>         unsigned int domain, bus, slot, func;
>> -       struct pci_bus *pci_bus;
>>         struct pci_dev *pci_dev;
>>         char str[64];
>>
>> @@ -1032,13 +1031,8 @@ static int pcifront_detach_devices(struct pcifront_device *pdev)
>>                         goto out;
>>                 }
>>
>> -               pci_bus = pci_find_bus(domain, bus);
>> -               if (!pci_bus) {
>> -                       dev_dbg(&pdev->xdev->dev, "Cannot get bus %04x:%02x\n",
>> -                               domain, bus);
>> -                       continue;
>> -               }
>> -               pci_dev = pci_get_slot(pci_bus, PCI_DEVFN(slot, func));
>> +               pci_dev = pci_get_domain_bus_and_slot(domain, bus,
>> +                               PCI_DEVFN(slot, func));
>>                 if (!pci_dev) {
>>                         dev_dbg(&pdev->xdev->dev,
>>                                 "Cannot get PCI device %04x:%02x:%02x.%d\n",
>> --
>> 1.7.9.5
>>
> 
> .
> 


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Patch

diff --git a/arch/ia64/sn/kernel/io_common.c b/arch/ia64/sn/kernel/io_common.c
index fbb5f2f..8630875 100644
--- a/arch/ia64/sn/kernel/io_common.c
+++ b/arch/ia64/sn/kernel/io_common.c
@@ -229,7 +229,6 @@  void sn_pci_fixup_slot(struct pci_dev *dev, struct pcidev_info *pcidev_info,
 {
 	int segment = pci_domain_nr(dev->bus);
 	struct pcibus_bussoft *bs;
-	struct pci_bus *host_pci_bus;
 	struct pci_dev *host_pci_dev;
 	unsigned int bus_no, devfn;
 
@@ -245,8 +244,7 @@  void sn_pci_fixup_slot(struct pci_dev *dev, struct pcidev_info *pcidev_info,
 
 	bus_no = (pcidev_info->pdi_slot_host_handle >> 32) & 0xff;
 	devfn = pcidev_info->pdi_slot_host_handle & 0xffffffff;
- 	host_pci_bus = pci_find_bus(segment, bus_no);
- 	host_pci_dev = pci_get_slot(host_pci_bus, devfn);
+	host_pci_dev = pci_get_domain_bus_and_slot(segment, bus_no, devfn);
 
 	pcidev_info->host_pci_dev = host_pci_dev;
 	pcidev_info->pdi_linux_pcidev = dev;
diff --git a/drivers/gpu/vga/vgaarb.c b/drivers/gpu/vga/vgaarb.c
index 3df8fc0..b6852b7 100644
--- a/drivers/gpu/vga/vgaarb.c
+++ b/drivers/gpu/vga/vgaarb.c
@@ -1066,7 +1066,6 @@  static ssize_t vga_arb_write(struct file *file, const char __user * buf,
 		}
 
 	} else if (strncmp(curr_pos, "target ", 7) == 0) {
-		struct pci_bus *pbus;
 		unsigned int domain, bus, devfn;
 		struct vga_device *vgadev;
 
@@ -1085,19 +1084,11 @@  static ssize_t vga_arb_write(struct file *file, const char __user * buf,
 			pr_debug("vgaarb: %s ==> %x:%x:%x.%x\n", curr_pos,
 				domain, bus, PCI_SLOT(devfn), PCI_FUNC(devfn));
 
-			pbus = pci_find_bus(domain, bus);
-			pr_debug("vgaarb: pbus %p\n", pbus);
-			if (pbus == NULL) {
-				pr_err("vgaarb: invalid PCI domain and/or bus address %x:%x\n",
-					domain, bus);
-				ret_val = -ENODEV;
-				goto done;
-			}
-			pdev = pci_get_slot(pbus, devfn);
+			pdev = pci_get_domain_bus_and_slot(domain, bus, devfn);
 			pr_debug("vgaarb: pdev %p\n", pdev);
 			if (!pdev) {
-				pr_err("vgaarb: invalid PCI address %x:%x\n",
-					bus, devfn);
+				pr_err("vgaarb: invalid PCI address %x:%x:%x\n",
+					domain, bus, devfn);
 				ret_val = -ENODEV;
 				goto done;
 			}
diff --git a/drivers/pci/hotplug/cpcihp_generic.c b/drivers/pci/hotplug/cpcihp_generic.c
index 81af764..a6a71c4 100644
--- a/drivers/pci/hotplug/cpcihp_generic.c
+++ b/drivers/pci/hotplug/cpcihp_generic.c
@@ -154,12 +154,8 @@  static int __init cpcihp_generic_init(void)
 	if(!r)
 		return -EBUSY;
 
-	bus = pci_find_bus(0, bridge_busnr);
-	if (!bus) {
-		err("Invalid bus number %d", bridge_busnr);
-		return -EINVAL;
-	}
-	dev = pci_get_slot(bus, PCI_DEVFN(bridge_slot, 0));
+	dev = pci_get_domain_bus_and_slot(0, bridge_busnr,
+					  PCI_DEVFN(bridge_slot, 0));
 	if(!dev || dev->hdr_type != PCI_HEADER_TYPE_BRIDGE) {
 		err("Invalid bridge device %s", bridge);
 		pci_dev_put(dev);
diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index 74bbaf8..c7d2969 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -152,15 +152,11 @@  failed1:
 static void virtfn_remove(struct pci_dev *dev, int id, int reset)
 {
 	char buf[VIRTFN_ID_LEN];
-	struct pci_bus *bus;
 	struct pci_dev *virtfn;
 	struct pci_sriov *iov = dev->sriov;
 
-	bus = pci_find_bus(pci_domain_nr(dev->bus), virtfn_bus(dev, id));
-	if (!bus)
-		return;
-
-	virtfn = pci_get_slot(bus, virtfn_devfn(dev, id));
+	virtfn = pci_get_domain_bus_and_slot(pci_domain_nr(dev->bus),
+			virtfn_bus(dev, id), virtfn_devfn(dev, id));
 	if (!virtfn)
 		return;
 
diff --git a/drivers/pci/xen-pcifront.c b/drivers/pci/xen-pcifront.c
index d6cc62c..def8d0b 100644
--- a/drivers/pci/xen-pcifront.c
+++ b/drivers/pci/xen-pcifront.c
@@ -982,7 +982,6 @@  static int pcifront_detach_devices(struct pcifront_device *pdev)
 	int err = 0;
 	int i, num_devs;
 	unsigned int domain, bus, slot, func;
-	struct pci_bus *pci_bus;
 	struct pci_dev *pci_dev;
 	char str[64];
 
@@ -1032,13 +1031,8 @@  static int pcifront_detach_devices(struct pcifront_device *pdev)
 			goto out;
 		}
 
-		pci_bus = pci_find_bus(domain, bus);
-		if (!pci_bus) {
-			dev_dbg(&pdev->xdev->dev, "Cannot get bus %04x:%02x\n",
-				domain, bus);
-			continue;
-		}
-		pci_dev = pci_get_slot(pci_bus, PCI_DEVFN(slot, func));
+		pci_dev = pci_get_domain_bus_and_slot(domain, bus,
+				PCI_DEVFN(slot, func));
 		if (!pci_dev) {
 			dev_dbg(&pdev->xdev->dev,
 				"Cannot get PCI device %04x:%02x:%02x.%d\n",