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Cc:     <linux-pci@vger.kernel.org>, <keith.busch@intel.com>,
        <Austin.Bolen@dell.com>, <Shyam.Iyer@dell.com>,
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From:   <Alex_Gagniuc@Dellteam.com>
To:     <helgaas@kernel.org>, <mr.nuke.me@gmail.com>
Subject: Re: [PATCH v2] PCI/MSI: Don't touch MSI bits when the PCI device is
 disconnected
Thread-Topic: [PATCH v2] PCI/MSI: Don't touch MSI bits when the PCI device is
 disconnected
Thread-Index: AQHUT50UQ290XPGvJEGnaSTTjbCF+g==
Date:   Thu, 27 Dec 2018 19:28:55 +0000
Message-ID: <4bc22b1696f345e483a21da16ac4b745@ausx13mps321.AMER.DELL.COM>
References: <20180918221501.13112-1-mr.nuke.me@gmail.com>
 <20181107234257.GC41183@google.com> <20181108200855.GE41183@google.com>
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On 11/8/18 2:09 PM, Bjorn Helgaas wrote:=0A=
> =0A=
> [EXTERNAL EMAIL]=0A=
> Please report any suspicious attachments, links, or requests for sensitiv=
e information.=0A=
> =0A=
> =0A=
> [+cc Jonathan, Greg, Lukas, Russell, Sam, Oliver for discussion about=0A=
> PCI error recovery in general]=0A=
> =0A=
> On Wed, Nov 07, 2018 at 05:42:57PM -0600, Bjorn Helgaas wrote:=0A=
>> On Tue, Sep 18, 2018 at 05:15:00PM -0500, Alexandru Gagniuc wrote:=0A=
>>> When a PCI device is gone, we don't want to send IO to it if we can=0A=
>>> avoid it. We expose functionality via the irq_chip structure. As=0A=
>>> users of that structure may not know about the underlying PCI device,=
=0A=
>>> it's our responsibility to guard against removed devices.=0A=
>>>=0A=
>>> .irq_write_msi_msg() is already guarded inside __pci_write_msi_msg().=
=0A=
>>> .irq_mask/unmask() are not. Guard them for completeness.=0A=
>>>=0A=
>>> For example, surprise removal of a PCIe device triggers teardown. This=
=0A=
>>> touches the irq_chips ops some point to disable the interrupts. I/O=0A=
>>> generated here can crash the system on firmware-first machines.=0A=
>>> Not triggering the IO in the first place greatly reduces the=0A=
>>> possibility of the problem occurring.=0A=
>>>=0A=
>>> Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>=0A=
>>=0A=
>> Applied to pci/misc for v4.21, thanks!=0A=
> =0A=
> I'm having second thoughts about this. =0A=
=0A=
Do we have a verdict on this? If you don't like this approach, then I'll =
=0A=
have to fix the problem in some other way, but the problem still needs =0A=
to be fixed.=0A=
=0A=
Alex=0A=