5.4.12 bnxt_en: Unable do read adapter's DSN

5.4.12 bnxt_en: Unable do read adapter's DSN

[Marc Smith]

Hi,

I'm using the 'bnxt_en' driver with vanilla Linux 5.4.12. I have a
Broadcom P225p 10/25 GbE adapter. I previously used this adapter with
Linux 4.14.120 with no issues. Now with 5.4.12 I observe the following
kernel messages during initialization:
...
[    2.605878] Broadcom NetXtreme-C/E driver bnxt_en v1.10.0
[    2.618302] bnxt_en 0000:00:03.0 (unnamed net_device)
(uninitialized): Unable do read adapter's DSN
[    2.622295] bnxt_en: probe of 0000:00:03.0 failed with error -95
[    2.632808] bnxt_en 0000:00:0a.0 (unnamed net_device)
(uninitialized): Unable do read adapter's DSN
[    2.637043] bnxt_en: probe of 0000:00:0a.0 failed with error -95
...

Looks like this comes from bnxt_pcie_dsn_get() in
drivers/net/ethernet/broadcom/bnxt/bnxt.c:
...
        int pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_DSN);
        u32 dw;

        if (!pos) {
                netdev_info(bp->dev, "Unable do read adapter's DSN");
                return -EOPNOTSUPP;
        }
...

And this appears to be related to newer functionality that was not
present in Linux 4.14.x. I am using the P225p via PCI passthrough from
a QEMU/KVM host. I do not have SR-IOV enabled on the card, so not
passing VF's through to the VM (only the PF's).

The card works in the host platform / hypervisor OS (CentOS 7) but
that of course is using the RHEL 3.10.x variant.


I guess my question is:
- Is it expected that a DSN (device serial number) should be available
(fetched via "pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_DSN)) when
the card is passed through into a QEMU/KVM (PCI pass through)? In
other words, is there a problem with my setup/card where the driver
should expect to read a DSN from inside of a virtual machine?
- Or is it normal for a DSN to not be available inside of the virtual
machine guest OS, and the 'bnxt_en' driver needs to be modified to
handle this case? I noticed in the upstream driver (direct from
Broadcom, bnxt_1.10.0-214.0.253.1) that bnxt_pcie_dsn_get() now
resides in bnxt_vfr.c and is called from bnxt_vf_reps_create() (rather
than bnxt_init_one() in 5.4.12).

Any help/advice would be greatly appreciated, thanks in advance.


--Marc

Re: 5.4.12 bnxt_en: Unable do read adapter's DSN

[Michael Chan]

On Thu, Jan 16, 2020 at 2:08 PM Marc Smith <msmith626@gmail.com> wrote:
>
> Hi,
>
> I'm using the 'bnxt_en' driver with vanilla Linux 5.4.12. I have a
> Broadcom P225p 10/25 GbE adapter. I previously used this adapter with
> Linux 4.14.120 with no issues. Now with 5.4.12 I observe the following
> kernel messages during initialization:
> ...
> [    2.605878] Broadcom NetXtreme-C/E driver bnxt_en v1.10.0
> [    2.618302] bnxt_en 0000:00:03.0 (unnamed net_device)
> (uninitialized): Unable do read adapter's DSN
> [    2.622295] bnxt_en: probe of 0000:00:03.0 failed with error -95
> [    2.632808] bnxt_en 0000:00:0a.0 (unnamed net_device)
> (uninitialized): Unable do read adapter's DSN
> [    2.637043] bnxt_en: probe of 0000:00:0a.0 failed with error -95
> ...

I have received a similar report about this issue recently.  I believe
some kernels are not configured to read extended configuration space
and so the driver's call to read the DSN would fail on such a kernel.
This failure should not be considered a fatal error and the driver
should continue to load.  I will send out a driver patch to fix this
very shortly.

Thanks.

Re: 5.4.12 bnxt_en: Unable do read adapter's DSN

[Marc Smith]

On Thu, Jan 16, 2020 at 5:19 PM Michael Chan <michael.chan@broadcom.com> wrote:
>
> On Thu, Jan 16, 2020 at 2:08 PM Marc Smith <msmith626@gmail.com> wrote:
> >
> > Hi,
> >
> > I'm using the 'bnxt_en' driver with vanilla Linux 5.4.12. I have a
> > Broadcom P225p 10/25 GbE adapter. I previously used this adapter with
> > Linux 4.14.120 with no issues. Now with 5.4.12 I observe the following
> > kernel messages during initialization:
> > ...
> > [    2.605878] Broadcom NetXtreme-C/E driver bnxt_en v1.10.0
> > [    2.618302] bnxt_en 0000:00:03.0 (unnamed net_device)
> > (uninitialized): Unable do read adapter's DSN
> > [    2.622295] bnxt_en: probe of 0000:00:03.0 failed with error -95
> > [    2.632808] bnxt_en 0000:00:0a.0 (unnamed net_device)
> > (uninitialized): Unable do read adapter's DSN
> > [    2.637043] bnxt_en: probe of 0000:00:0a.0 failed with error -95
> > ...
>
> I have received a similar report about this issue recently.  I believe
> some kernels are not configured to read extended configuration space
> and so the driver's call to read the DSN would fail on such a kernel.
> This failure should not be considered a fatal error and the driver
> should continue to load.  I will send out a driver patch to fix this
> very shortly.

Thanks Michael for providing a patch so quickly! I'll try the patches
you posted in just a bit.

I'm curious though about your comment: Is there in a fact a kernel
config option I can enable for "extended configuration space support"?
I looked through the PCI support options in the kernel config menu on
5.4.x but nothing jumped out at me that sounded similar to this.

--Marc


>
> Thanks.

Re: 5.4.12 bnxt_en: Unable do read adapter's DSN

[Michael Chan]

On Fri, Jan 17, 2020 at 8:04 AM Marc Smith <msmith626@gmail.com> wrote:

> I'm curious though about your comment: Is there in a fact a kernel
> config option I can enable for "extended configuration space support"?
> I looked through the PCI support options in the kernel config menu on
> 5.4.x but nothing jumped out at me that sounded similar to this.
>

As I said, I received a similar report about this issue and they
specifically reported that PCIe extended config space was not enabled
in their kernel.  I believe it is CONFIG_PCI_MMCONFIG that will enable
access to extended config space.  It's also possible that during
kernel boot time, the MMCONFIG base address could not be determined in
their environment.

Thanks.