linux-kernel - [PATCH] vfio: pci: Advertise INTx only if LINE is connected

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Message-ID: <174231895238.2295.12586708771396482526.stgit@linux.ibm.com>
Date: Tue, 18 Mar 2025 17:29:21 +0000
From: Shivaprasad G Bhat <sbhat@...ux.ibm.com>
To: alex.williamson@...hat.com, jgg@...pe.ca, kevin.tian@...el.com
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org, yi.l.liu@...el.com,
        Yunxiang.Li@....com, pstanner@...hat.com, maddy@...ux.ibm.com,
        linuxppc-dev@...ts.ozlabs.org, sbhat@...ux.ibm.com
Subject: [PATCH] vfio: pci: Advertise INTx only if LINE is connected

On POWER systems, when the device is behind the io expander,
not all PCI slots would have the PCI_INTERRUPT_LINE connected.
The firmware assigns a valid PCI_INTERRUPT_PIN though. In such
configuration, the irq_info ioctl currently advertizes the
irq count as 1 as the PCI_INTERRUPT_PIN is valid.

The patch adds the additional check[1] if the irq is assigned
for the PIN which is done iff the LINE is connected.

[1]: https://lore.kernel.org/qemu-devel/20250131150201.048aa3bf.alex.williamson@redhat.com/

Signed-off-by: Shivaprasad G Bhat <sbhat@...ux.ibm.com>
Suggested-By: Alex Williamson <alex.williamson@...hat.com>
---
 drivers/vfio/pci/vfio_pci_core.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index 586e49efb81b..4ce70f05b4a8 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -734,6 +734,10 @@ static int vfio_pci_get_irq_count(struct vfio_pci_core_device *vdev, int irq_typ
 			return 0;
 
 		pci_read_config_byte(vdev->pdev, PCI_INTERRUPT_PIN, &pin);
+#if IS_ENABLED(CONFIG_PPC64)
+		if (!vdev->pdev->irq)
+			pin = 0;
+#endif
 
 		return pin ? 1 : 0;
 	} else if (irq_type == VFIO_PCI_MSI_IRQ_INDEX) {