On Wed, Jun 26, 2024 at 10:10:39AM -0500, Bjorn Helgaas wrote:
> 1) Capitalize subject to match history
What do you mean here? I got the "PCI: hv: ..." format from recent
commits. "PCI" is capitalized. You want to to capitalize "fix"?
> 2) Say something more specific than "fix reading ..."
>
> Apparently this returns garbage in some case where you want to return
> zero?
Yes. *val is not changed in the old code, so garbage is returned.
Here is the updated commit message. I can resend once you confirm you're
happy with it.
PCI: hv: Fix reading of 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 this case.
Fixes: 4daace0d8ce8 ("PCI: hv: Add paravirtual PCI front-end for Microsoft Hyper-V VMs")
Cc: stable@xxxxxxxxxx
Signed-off-by: Wei Liu <wei.liu@xxxxxxxxxx>
Thanks,
Wei.
>
> On Fri, Jun 21, 2024 at 09:00:18PM +0000, Wei Liu wrote:
> > 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.
> >
> > Fixes: 4daace0d8ce8 ("PCI: hv: Add paravirtual PCI front-end for Microsoft Hyper-V VMs")
> > Cc: stable@xxxxxxxxxx
> > Signed-off-by: Wei Liu <wei.liu@xxxxxxxxxx>
> > ---
> > v2:
> > * Change the commit subject line and message
> > * Change the code according to feedback
> > ---
> > 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..cdd5be16021d 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 + 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
> > --
> > 2.43.0
> >
