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Subject[PATCH v2] PCI/MSI: Don't touch MSI bits when the PCI device is disconnected
Date
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@gmail.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 */
--
2.17.1
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