[PATCH v2] PCI/MSI: Don't touch MSI bits when the PCI device is disconnected

[Alex_Gagniuc at Dellteam.com]

On 11/8/18 2:09 PM, Bjorn Helgaas wrote:
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> [+cc Jonathan, Greg, Lukas, Russell, Sam, Oliver for discussion about
> PCI error recovery in general]
> 
> On Wed, Nov 07, 2018 at 05:42:57PM -0600, Bjorn Helgaas wrote:
>> On Tue, Sep 18, 2018 at 05:15:00PM -0500, Alexandru Gagniuc wrote:
>>> When a PCI device is gone, we don't want to send IO to it if we can
>>> avoid it. We expose functionality via the irq_chip structure. As
>>> users of that structure may not know about the underlying PCI device,
>>> it's our responsibility to guard against removed devices.
>>>
>>> .irq_write_msi_msg() is already guarded inside __pci_write_msi_msg().
>>> .irq_mask/unmask() are not. Guard them for completeness.
>>>
>>> For example, surprise removal of a PCIe device triggers teardown. This
>>> touches the irq_chips ops some point to disable the interrupts. I/O
>>> generated here can crash the system on firmware-first machines.
>>> Not triggering the IO in the first place greatly reduces the
>>> possibility of the problem occurring.
>>>
>>> Signed-off-by: Alexandru Gagniuc <mr.nuke.me at gmail.com>
>>
>> Applied to pci/misc for v4.21, thanks!
> 
> I'm having second thoughts about this. 

Do we have a verdict on this? If you don't like this approach, then I'll 
have to fix the problem in some other way, but the problem still needs 
to be fixed.

Alex