This is intended as a non-functional change. It aims to simplify and
optimize pci_get_alias_group().
The purpose of pci_get_alias_group() is to find the set of devices on the
same bus that are not ACS isolated or part of the alias set. All of these
devices should share a group so pci_get_alias_group() will search that set
for an existing group to join.
pci_reachable_set() does the calculations for figuring out the set of
devices under the pci_bus_sem, which is better than repeatedly searching
across all PCI devices.
Once the set of devices is determined it is a quick pci_get_slot() to
search for any existing groups in the subset.
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
---
drivers/iommu/iommu.c | 137 ++++++++++++++----------------------------
1 file changed, 45 insertions(+), 92 deletions(-)
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index f98c25514bf912..5a8077d4b79d41 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1413,85 +1413,6 @@ int iommu_group_id(struct iommu_group *group)
}
EXPORT_SYMBOL_GPL(iommu_group_id);
-static struct iommu_group *get_pci_alias_group(struct pci_dev *pdev,
- unsigned long *devfns);
-
-/*
- * For multifunction devices which are not isolated from each other, find
- * all the other non-isolated functions and look for existing groups. For
- * each function, we also need to look for aliases to or from other devices
- * that may already have a group.
- */
-static struct iommu_group *get_pci_function_alias_group(struct pci_dev *pdev,
- unsigned long *devfns)
-{
- struct pci_dev *tmp = NULL;
- struct iommu_group *group;
-
- if (!pdev->multifunction || pci_acs_enabled(pdev, PCI_ACS_ISOLATED))
- return NULL;
-
- for_each_pci_dev(tmp) {
- if (tmp == pdev || tmp->bus != pdev->bus ||
- PCI_SLOT(tmp->devfn) != PCI_SLOT(pdev->devfn) ||
- pci_acs_enabled(tmp, PCI_ACS_ISOLATED))
- continue;
-
- group = get_pci_alias_group(tmp, devfns);
- if (group) {
- pci_dev_put(tmp);
- return group;
- }
- }
-
- return NULL;
-}
-
-/*
- * Look for aliases to or from the given device for existing groups. DMA
- * aliases are only supported on the same bus, therefore the search
- * space is quite small (especially since we're really only looking at pcie
- * device, and therefore only expect multiple slots on the root complex or
- * downstream switch ports). It's conceivable though that a pair of
- * multifunction devices could have aliases between them that would cause a
- * loop. To prevent this, we use a bitmap to track where we've been.
- */
-static struct iommu_group *get_pci_alias_group(struct pci_dev *pdev,
- unsigned long *devfns)
-{
- struct pci_dev *tmp = NULL;
- struct iommu_group *group;
-
- if (test_and_set_bit(pdev->devfn & 0xff, devfns))
- return NULL;
-
- group = iommu_group_get(&pdev->dev);
- if (group)
- return group;
-
- for_each_pci_dev(tmp) {
- if (tmp == pdev || tmp->bus != pdev->bus)
- continue;
-
- /* We alias them or they alias us */
- if (pci_devs_are_dma_aliases(pdev, tmp)) {
- group = get_pci_alias_group(tmp, devfns);
- if (group) {
- pci_dev_put(tmp);
- return group;
- }
-
- group = get_pci_function_alias_group(tmp, devfns);
- if (group) {
- pci_dev_put(tmp);
- return group;
- }
- }
- }
-
- return NULL;
-}
-
/*
* Generic device_group call-back function. It just allocates one
* iommu-group per device.
@@ -1523,25 +1444,57 @@ struct iommu_group *generic_single_device_group(struct device *dev)
}
EXPORT_SYMBOL_GPL(generic_single_device_group);
+static bool pci_devs_are_same_group(struct pci_dev *deva, struct pci_dev *devb)
+{
+ /*
+ * This is allowed to return cycles: a,b -> b,c -> c,a can be aliases.
+ */
+ if (pci_devs_are_dma_aliases(deva, devb))
+ return true;
+
+ /*
+ * If any function in a multi function device does not have ACS
+ * isolation turned on then the specs allows it to loop back internally
+ * to another function.
+ */
+ if ((deva->multifunction || devb->multifunction) &&
+ PCI_SLOT(deva->devfn) == PCI_SLOT(devb->devfn)) {
+ if (!pci_acs_enabled(deva, PCI_ACS_ISOLATED) ||
+ !pci_acs_enabled(devb, PCI_ACS_ISOLATED))
+ return true;
+ }
+ return false;
+}
+
static struct iommu_group *pci_get_alias_group(struct pci_dev *pdev)
{
- struct iommu_group *group;
- u64 devfns[4] = { 0 };
+ struct pci_alias_set devfns;
+ unsigned int devfn;
/*
- * Look for existing groups on device aliases. If we alias another
- * device or another device aliases us, use the same group.
+ * Look for existing groups on device aliases and multi-function ACS. If
+ * we alias another device or another device aliases us, use the same
+ * group.
+ *
+ * pci_reachable_set() should return the same bitmap if called for any
+ * device in the set and we want all devices in the set to have the same
+ * group.
*/
- group = get_pci_alias_group(pdev, (unsigned long *)devfns);
- if (group)
- return group;
+ pci_reachable_set(pdev, &devfns, pci_devs_are_same_group);
+ /* start is known to have iommu_group_get() == NULL */
+ __clear_bit(pdev->devfn & 0xFF, devfns.devfns);
+ for_each_set_bit(devfn, devfns.devfns,
+ sizeof(devfns.devfns) * BITS_PER_BYTE) {
+ struct iommu_group *group;
+ struct pci_dev *pdev_slot;
- /*
- * Look for existing groups on non-isolated functions on the same
- * slot and aliases of those funcions, if any. No need to clear
- * the search bitmap, the tested devfns are still valid.
- */
- return get_pci_function_alias_group(pdev, (unsigned long *)devfns);
+ pdev_slot = pci_get_slot(pdev->bus, devfn);
+ group = iommu_group_get(&pdev_slot->dev);
+ pci_dev_put(pdev_slot);
+ if (group)
+ return group;
+ }
+ return NULL;
}
static struct iommu_group *pci_hierarchy_group(struct pci_dev *pdev)
--
2.43.0
