On Sun, Sep 13, 2026 at 03:10:39PM -0700, [email protected] wrote:
> From: Mukesh R <[email protected]>
>
> Hyper-V Discrete Device Assignment (DDA) does not support legacy (INTX)
> interrupts. When PCI_INTERRUPT_PIN is read, the pci-hyperv controller,
> which captures configuration space accesses, returns 0 to the caller.
>
> However, the current code only captures 8bit read access, thus 16bit/32bit
> are missed, forwarded to the host/HW, and may yield a non zero value.
>
> This fix addresses this issue, and makes sure that PCI_INTERRUPT_PIN is
> hardwired to 0, while the other bytes, are those returned by the host/HW.
>
> Signed-off-by: Asher Kariv <[email protected]>
> Signed-off-by: Mukesh R <[email protected]>
> Signed-off-by: Wei Liu <[email protected]>
> ---
> drivers/pci/controller/pci-hyperv.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/pci/controller/pci-hyperv.c
> b/drivers/pci/controller/pci-hyperv.c
> index 89816a2bd7cd..e6db82413add 100644
> --- a/drivers/pci/controller/pci-hyperv.c
> +++ b/drivers/pci/controller/pci-hyperv.c
> @@ -1240,6 +1240,16 @@ static void _hv_pcifront_read_config(struct hv_pci_dev
> *hpdev, int where,
> mb();
> }
> spin_unlock_irqrestore(&hbus->config_lock, flags);
> +
> + /*
> + * Make sure PCI_INTERRUPT_PIN is hard-wired to 0, since it
> + * may be read using a 32bit read, which is skipped by the
> + * above emulation.
> + */
> + if (where <= PCI_INTERRUPT_PIN &&
> + PCI_INTERRUPT_PIN < (where + size))
> + *((char *)val + PCI_INTERRUPT_PIN - where) = 0;
> + }
Please ignore this version. A new version will be sent out to add back the
opening brace.
Wei
> } else {
> dev_err(dev, "Attempt to read beyond a function's config
> space.\n");
> }
> --
> 2.53.0
>
