From be20f6b063f51cd77d071b803ee24f23200dc559 Mon Sep 17 00:00:00 2001
From: KarimAllah Ahmed <karahmed@amazon.de>
Date: Wed, 17 Jan 2018 19:30:29 +0100
Subject: [PATCH] PCI/IOV: Skip INTx config reads for VFs
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Git-commit: be20f6b063f51cd77d071b803ee24f23200dc559
Patch-mainline: v4.17-rc1
References: FATE#326145

Per PCIe r4.0, sec 9.2.1.4, VFs can not implement INTX, and their Interrupt
Line and Interrupt Pin registers must be RO Zero.  Some devices have
thousands of VFs, so skip reading the registers as an optimization.

Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
Signed-off-by: Jan H. Schönherr <jschoenh@amazon.de>
[bhelgaas: changelog, comment]
Signed-off-by: Bjorn Helgaas <helgaas@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/pci/probe.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 489660d0d384..a1cddca37793 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1230,6 +1230,13 @@ static void pci_read_irq(struct pci_dev *dev)
 {
 	unsigned char irq;
 
+	/* VFs are not allowed to use INTx, so skip the config reads */
+	if (dev->is_virtfn) {
+		dev->pin = 0;
+		dev->irq = 0;
+		return;
+	}
+
 	pci_read_config_byte(dev, PCI_INTERRUPT_PIN, &irq);
 	dev->pin = irq;
 	if (irq)
-- 
2.19.2