PCI: hv: Return zero, not garbage, when reading PCI_INTERRUPT_PIN

The intent of the code snippet is to always return 0 for both
PCI_INTERRUPT_LINE and PCI_INTERRUPT_PIN.

The check misses PCI_INTERRUPT_PIN. This patch fixes that.

This is discovered by this call in VFIO:

    pci_read_config_byte(vdev->pdev, PCI_INTERRUPT_PIN, &pin);

The old code does not set *val to 0 because it misses the check for
PCI_INTERRUPT_PIN. Garbage is returned in that case.

Fixes: 4daace0 ("PCI: hv: Add paravirtual PCI front-end for Microsoft Hyper-V VMs")
Link: https://lore.kernel.org/linux-pci/[email protected]
Signed-off-by: Wei Liu <[email protected]>
Signed-off-by: Krzysztof Wilczyński <[email protected]>
Reviewed-by: Michael Kelley <[email protected]>
Cc: [email protected]

Author: liuw

drivers/pci/controller/pci-hyperv.c

@@ -1130,8 +1130,8 @@ static void _hv_pcifront_read_config(struct hv_pci_dev *hpdev, int where,
 		   PCI_CAPABILITY_LIST) {
 		/* ROM BARs are unimplemented */
 		*val = 0;
-	} else if (where >= PCI_INTERRUPT_LINE && where + size <=
-		   PCI_INTERRUPT_PIN) {
+	} else if ((where >= PCI_INTERRUPT_LINE && where + size <= PCI_INTERRUPT_PIN) ||
+		   (where >= PCI_INTERRUPT_PIN && where + size <= PCI_MIN_GNT)) {
 		/*
 		 * Interrupt Line and Interrupt PIN are hard-wired to zero
 		 * because this front-end only supports message-signaled