PCI: Differentiate ACS controllable from enabled (83db7e0b) · Commits · 戴 / test

We currently misinterpret that in order for an ACS feature to be enabled it must be set in the control field. In reality, this means that the feature is not only enabled, but controllable. Many of the ACS capability bits are not required if the device behaves by default in the way specified when both the capability and control bit are set and does not support or allow the alternate mode. We therefore need to check the capabilities and mask out flags that are enabled but not controllable. Egress control seems to be the only flag which is purely optional. Signed-off-by:

Alex Williamson <alex.williamson@redhat.com> Signed-off-by:

Bjorn Helgaas <bhelgaas@google.com> Acked-by:

Donald Dutile <ddutile@redhat.com>

drivers/pci/pci.c

+9 −4

Original line number	Diff line number	Diff line
		@@ -2362,12 +2362,20 @@ void pci_enable_acs(struct pci_dev *dev)
		static bool pci_acs_flags_enabled(struct pci_dev *pdev, u16 acs_flags)
		{
		int pos;
		u16 ctrl;
		u16 cap, ctrl;

		pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_ACS);
		if (!pos)
		return false;

		/*
		* Except for egress control, capabilities are either required
		* or only required if controllable. Features missing from the
		* capability field can therefore be assumed as hard-wired enabled.
		*/
		pci_read_config_word(pdev, pos + PCI_ACS_CAP, &cap);
		acs_flags &= (cap \| PCI_ACS_EC);

		pci_read_config_word(pdev, pos + PCI_ACS_CTRL, &ctrl);
		return (ctrl & acs_flags) == acs_flags;
		}
		@@ -2442,9 +2450,6 @@ bool pci_acs_enabled(struct pci_dev *pdev, u16 acs_flags)
		if (!pdev->multifunction)
		break;

		acs_flags &= (PCI_ACS_RR \| PCI_ACS_CR \|
		PCI_ACS_EC \| PCI_ACS_DT);

		return pci_acs_flags_enabled(pdev, acs_flags);
		}

Admin message