[PATCH 2/3] pci/hotplug/pnv-php: Disable surprise hotplug capability on conflicts

[Gavin Shan]

On Thu, Feb 16, 2017 at 03:31:48PM +1100, Andrew Donnellan wrote:
>On 16/02/17 10:22, Gavin Shan wrote:
>>The root port or PCIe switch downstream port might have been associated
>>with driver other than pnv-php. The MSI or MSIx might also have been
>>enabled by that driver (e.g. pcieport_drv). Attempt to enable MSI incurs
>>below backtrace:
>>
>> PowerPC PowerNV PCI Hotplug Driver version: 0.1
>> ------------[ cut here ]------------
>> WARNING: CPU: 19 PID: 1004 at drivers/pci/msi.c:1071 \
>>                              __pci_enable_msi_range+0x84/0x4e0
>> NIP [c000000000665c34] __pci_enable_msi_range+0x84/0x4e0
>> LR [c000000000665c24] __pci_enable_msi_range+0x74/0x4e0
>> Call Trace:
>> [c000000384d67600] [c000000000665c24] __pci_enable_msi_range+0x74/0x4e0
>> [c000000384d676e0] [d00000000aa31b04] pnv_php_register+0x564/0x5a0 [pnv_php]
>> [c000000384d677c0] [d00000000aa31658] pnv_php_register+0xb8/0x5a0 [pnv_php]
>> [c000000384d678a0] [d00000000aa31658] pnv_php_register+0xb8/0x5a0 [pnv_php]
>> [c000000384d67980] [d00000000aa31dfc] pnv_php_init+0x60/0x98 [pnv_php]
>> [c000000384d679f0] [c00000000000cfdc] do_one_initcall+0x6c/0x1d0
>> [c000000384d67ab0] [c000000000b92354] do_init_module+0x94/0x254
>> [c000000384d67b40] [c00000000019719c] load_module+0x258c/0x2c60
>> [c000000384d67d30] [c000000000197bb0] SyS_finit_module+0xf0/0x170
>> [c000000384d67e30] [c00000000000b184] system_call+0x38/0xe0
>>360aebd85a4c
>>This fixes the issue by skipping enabling the surprise hotplug
>>capability if the MSI or MSIx on the PCI slot's upstream port has
>>been enabled by other driver.
>>
>>Cc: <stable at vger.kernel.org> # v4.9+
>>Fixes: 360aebd85a4c ("drivers/pci/hotplug: Support surprise hotplug in powernv driver")
>>Signed-off-by: Gavin Shan <gwshan at linux.vnet.ibm.com>
>
>Should this print something to the kernel log to indicate that surprise
>hotplug is unavailable?
>

I don't think it's necessary as the situation can be known from lspci
and /proc/interrupts easily. Otherwise, we could add pr_warn_once()
to print the warning message for once, not on all slots.

Thanks,
Gavin