pcie: kernel log - BAR 15: no space for... BAR 15: failed to assign..

[Muni Sekhar]

On Tue, Feb 11, 2020 at 8:10 PM Bjorn Helgaas <helgaas at kernel.org> wrote:
>
> On Tue, Feb 11, 2020 at 07:36:00PM +0530, Muni Sekhar wrote:
> > On Tue, Feb 11, 2020 at 3:58 AM Bjorn Helgaas <helgaas at kernel.org> wrote:
> > > On Sun, Feb 09, 2020 at 07:59:41AM +0530, Muni Sekhar wrote:
> > > > Hi all,
> > > >
> > > > After rebooting the system following messages are seen in dmesg.
> > > > Not sure if these indicate a problem. Can some one look at these and
> > > > confirm if this is problem or can be ignored ?
> > > >
> > > > Also any suggestions as to what would cause this?
> > > >
> > > > [    1.084728] pci 0000:00:1c.0: BAR 15: no space for [mem size
> > > > 0x00200000 64bit pref]
> > > > [    1.084813] pci 0000:00:1c.0: BAR 15: failed to assign [mem size
> > > > 0x00200000 64bit pref]
> > > > [    1.084890] pci 0000:00:1c.2: BAR 14: no space for [mem size 0x00200000]
> > > > [    1.084949] pci 0000:00:1c.2: BAR 14: failed to assign [mem size 0x00200000]
> > > > [    1.085037] pci 0000:00:1c.2: BAR 15: no space for [mem size
> > > > 0x00200000 64bit pref]
> > > > [    1.085108] pci 0000:00:1c.2: BAR 15: failed to assign [mem size
> > > > 0x00200000 64bit pref]
> > > > [    1.085199] pci 0000:00:1c.3: BAR 15: no space for [mem size
> > > > 0x00200000 64bit pref]
> > > > [    1.085270] pci 0000:00:1c.3: BAR 15: failed to assign [mem size
> > > > 0x00200000 64bit pref]
> > > > [    1.085343] pci 0000:00:1c.0: BAR 13: assigned [io  0x1000-0x1fff]
> > > > [    1.085403] pci 0000:00:1c.2: BAR 13: assigned [io  0x2000-0x2fff]
> > > > [    1.085470] pci 0000:00:1c.3: BAR 15: no space for [mem size
> > > > 0x00200000 64bit pref]
> > > > [    1.085540] pci 0000:00:1c.3: BAR 15: failed to assign [mem size
> > > > 0x00200000 64bit pref]
> > > > [    1.085613] pci 0000:00:1c.2: BAR 14: no space for [mem size 0x00200000]
> > > > [    1.085672] pci 0000:00:1c.2: BAR 14: failed to assign [mem size 0x00200000]
> > > > [    1.085738] pci 0000:00:1c.2: BAR 15: no space for [mem size
> > > > 0x00200000 64bit pref]
> > > > [    1.085808] pci 0000:00:1c.2: BAR 15: failed to assign [mem size
> > > > 0x00200000 64bit pref]
> > > > [    1.085884] pci 0000:00:1c.0: BAR 15: no space for [mem size
> > > > 0x00200000 64bit pref]
> > > > [    1.085954] pci 0000:00:1c.0: BAR 15: failed to assign [mem size
> > > > 0x00200000 64bit pref]
> > > > [    1.086026] pci 0000:00:1c.0: PCI bridge to [bus 01]
> > > > [    1.086083] pci 0000:00:1c.0:   bridge window [io  0x1000-0x1fff]
> > > > [    1.086144] pci 0000:00:1c.0:   bridge window [mem 0xd0400000-0xd07fffff]
> > >
> > > The "no space" and "failed to assign" messages are all for bridge
> > > windows (13 is the I/O window, 14 is the MMIO window, 15 is the MMIO
> > > pref window).  I can't tell if you have any devices below these
> > > bridges (lspci would show them).  If you don't have any devices below
> > > these bridges, you can ignore the messages.
> >
> > I have the devices below these bridges. FPGA endpoint is connected to
> > '00:1c.0 PCI bridge' and Ethernet controller is connected to '00:1c.3
> > PCI bridge'.
> > Does these messages impact the functionality of the connected devices?
>
> Yes.  We tried to allocate 0x00200000 of prefetchable MMIO to 00:1c.0
> for use by the FPGA endpoint.  But this failed, so there is no
> prefetchable MMIO available for the FPGA.  The 0xd0400000-0xd07fffff
> non-prefetachable MMIO space *is* available for it.
>
> Similarly, we were unable to allocate 0x00200000 of prefetchable MMIO
> for the 00:1c.3 bridge for use by the ethernet controller.  I don't
> know what non-prefetchable MMIO space was allocated or what the NIC
> needs.
>
> "lspci -v" will show you what the FPGA and the NIC need.
>
> > If so what kind of impact and is there any solution for this?
>
> > Also, I'd like to know why "no space" and "failed to assign"
> > messages displayed?
>
> These messages mean we tried to allocate space for the bridges but we
> unable to do so.  This is because either the host bridge didn't have
> big enough apertures (on x86, these usually come from ACPI _CRS
> methods), or there's a bug in the Linux allocation algorithms.
>
> I can't tell anything more without seeing the complete dmesg log,
> which contains the host bridge aperture information and the BAR sizes
> of the FPGA and NIC.
Thank you for the clarification. dmesg log is attached.
If PCI bridge aperture is small, What is the most sensible way to proceed?

>
> Bjorn



-- 
Thanks,
Sekhar
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