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

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Date:   Wed, 7 Nov 2018 17:04:58 +0000
From:   "Derrick, Jonathan" <jonathan.derrick@...el.com>
To:     "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "mr.nuke.me@...il.com" <mr.nuke.me@...il.com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>
CC:     "alex_gagniuc@...lteam.com" <alex_gagniuc@...lteam.com>,
        "Busch, Keith" <keith.busch@...el.com>,
        "shyam_iyer@...l.com" <shyam_iyer@...l.com>,
        "austin_bolen@...l.com" <austin_bolen@...l.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] PCI/MSI: Don't touch MSI bits when the PCI device is
 disconnected

I found the same issue:
https://patchwork.ozlabs.org/patch/989272/

Tested-by: Jon Derrick <jonathan.derrick@...el.com>

On Mon, 2018-11-05 at 18:32 -0600, Alex G. wrote:
> ping
> 
> On 09/18/2018 05:15 PM, 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@...il.com>
> > ---
> >   drivers/pci/msi.c | 3 +++
> >   1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> > index f2ef896464b3..f31058fd2260 100644
> > --- a/drivers/pci/msi.c
> > +++ b/drivers/pci/msi.c
> > @@ -227,6 +227,9 @@ static void msi_set_mask_bit(struct irq_data
> > *data, u32 flag)
> >   {
> >   	struct msi_desc *desc = irq_data_get_msi_desc(data);
> >   
> > +	if (pci_dev_is_disconnected(msi_desc_to_pci_dev(desc)))
> > +		return;
> > +
> >   	if (desc->msi_attrib.is_msix) {
> >   		msix_mask_irq(desc, flag);
> >   		readl(desc->mask_base);		/* Flush
> > write to device */
> > 
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