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: 4daace0d8ce8 ("PCI: hv: Add paravirtual PCI front-end for Microsoft Hyper-V VMs")
Link: https://lore.kernel.org/linux-pci/20240701202606.129606-1-wei.liu@kernel.org
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Cc: stable@kernel.org

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 5992280e8110be900bb9a177296e39b6d8b55662..cdd5be16021dd4b71a07540382691af452a4842e 100644 (file)
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/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