PCI: add ACS validation utility

In a PCI environment, transactions aren't always required to reach
the root bus before being re-routed.  Intermediate switches between
an endpoint and the root bus can redirect DMA back downstream before
things like IOMMUs have a chance to intervene.  Legacy PCI is always
susceptible to this as it operates on a shared bus.  PCIe added a
new capability to describe and control this behavior, Access Control
Services, or ACS.

The utility function pci_acs_enabled() allows us to test the ACS
capabilities of an individual devices against a set of flags while
pci_acs_path_enabled() tests a complete path from a given downstream
device up to the specified upstream device.  We also include the
ability to add device specific tests as it's likely we'll see
devices that do not implement ACS, but want to indicate support
for various capabilities in this space.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/include/linux/pci.h b/include/linux/pci.h
index 39983be7b25b..dd7af0f37b3a 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1490,6 +1490,7 @@ enum pci_fixup_pass {
 #ifdef CONFIG_PCI_QUIRKS
 void pci_fixup_device(enum pci_fixup_pass pass, struct pci_dev *dev);
 struct pci_dev *pci_get_dma_source(struct pci_dev *dev);
+int pci_dev_specific_acs_enabled(struct pci_dev *dev, u16 acs_flags);
 #else
 static inline void pci_fixup_device(enum pci_fixup_pass pass,
                                     struct pci_dev *dev) {}
@@ -1497,6 +1498,11 @@ static inline struct pci_dev *pci_get_dma_source(struct pci_dev *dev)
 {
         return pci_dev_get(dev);
 }
+static inline int pci_dev_specific_acs_enabled(struct pci_dev *dev,
+                                               u16 acs_flags)
+{
+        return -ENOTTY;
+}
 #endif
 
 void __iomem *pcim_iomap(struct pci_dev *pdev, int bar, unsigned long maxlen);
@@ -1599,7 +1605,9 @@ static inline bool pci_is_pcie(struct pci_dev *dev)
 }
 
 void pci_request_acs(void);
-
+bool pci_acs_enabled(struct pci_dev *pdev, u16 acs_flags);
+bool pci_acs_path_enabled(struct pci_dev *start,
+                          struct pci_dev *end, u16 acs_flags);
 
 #define PCI_VPD_LRDT                    0x80    /* Large Resource Data Type */
 #define PCI_VPD_LRDT_ID(x)              (x | PCI_VPD_LRDT)