On Thu, Aug 16, 2018 at 09:13:03AM -0600, Alex Williamson wrote:
> static int pci_quirk_enable_intel_spt_pch_acs(struct pci_dev *dev)
> {
> int pos;
> + u16 std_ctrl;
> u32 cap, ctrl;
>
> if (!pci_quirk_intel_spt_pch_acs_match(dev))
> @@ -4621,6 +4628,18 @@ static int pci_quirk_enable_intel_spt_pch_acs(struct pci_dev *dev)
> if (!pos)
> return -ENOTTY;
>
> + /* If the std control word has bits set or is writable, do not quirk */
> + pci_read_config_word(dev, pos + PCI_ACS_CTRL, &std_ctrl);
> + if (std_ctrl)
> + return -ENOTTY;
> +
> + pci_write_config_word(dev, pos + PCI_ACS_CTRL, 0xff);
I don't know ACS well but could the above have some unwanted
side-effects, even if we write back zeroes below?
> + pci_read_config_word(dev, pos + PCI_ACS_CTRL, &std_ctrl);
> + if (std_ctrl) {
> + pci_write_config_word(dev, pos + PCI_ACS_CTRL, 0);
> + return -ENOTTY;
> + }
> +
> pci_read_config_dword(dev, pos + PCI_ACS_CAP, &cap);
> pci_read_config_dword(dev, pos + INTEL_SPT_ACS_CTRL, &ctrl);
>
