From: Wei Liu <wei.liu@xxxxxxxxxx> Sent: Thursday, June 20, 2024 6:48 PM
>
> The intent of the code snippet is to always return 0 for both fields.
> The check is wrong though. Fix 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 the second half of the check is
> incorrect.
>
> Fixes: 4daace0d8ce85 ("PCI: hv: Add paravirtual PCI front-end for Microsoft Hyper-V
> VMs")
> Cc: stable@xxxxxxxxxx
> Signed-off-by: Wei Liu <wei.liu@xxxxxxxxxx>
> ---
> drivers/pci/controller/pci-hyperv.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> index 5992280e8110..eec087c8f670 100644
> --- 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 == PCI_INTERRUPT_PIN) &&
> + size == 1) {
Any reason not to continue the pattern of the rest of the function,
and do the following to fix the bug?
} else if (where >= PCI_INTERRUPT_LINE && where + size <=
PCI_MIN_GNT) {
Your fix doesn't allow PCI_INTERRUPT_LINE and PCI_INTERRUPT_PIN
to be read together as a 2-byte access, though I don't know if that
matters.
I have a slight preference for the more consistent approach, but
don't really object to what you've done. Treat my idea as a
suggestion to consider, but if you want to go with your approach,
that's OK too.
Michael
> /*
> * Interrupt Line and Interrupt PIN are hard-wired to zero
> * because this front-end only supports message-signaled
> --
> 2.43.0
>
