Inherit the ARI Forwarding Enable on preserved bridges and update
pci_dev->ari_enabled accordingly during a Live Update. This ensures that
the preserved devices on the bridge's secondary bus can be identified
with the same expanded 8-bit function number after a Live Update.

Signed-off-by: David Matlack <dmatlack@google.com>
---
 drivers/pci/liveupdate.c | 18 ++++++++++++++++++
 drivers/pci/liveupdate.h |  6 ++++++
 drivers/pci/pci.c        |  8 +++++++-
 3 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/liveupdate.c b/drivers/pci/liveupdate.c
index e3cd6d76636c..6ab03bd548b3 100644
--- a/drivers/pci/liveupdate.c
+++ b/drivers/pci/liveupdate.c
@@ -132,6 +132,10 @@
  *    way after Live Update and ensures that IOMMU groups do not change. Note
  *    that a device will use its inherited ACS flags for the lifetime of its
  *    struct pci_dev (i.e. even after pci_liveupdate_finish()).
+ *
+ *  * The PCI core inherits ARI Forwarding Enable on all bridges with downstream
+ *    preserved devices to ensure that all preserved devices on the bridge's
+ *    secondary bus are addressable after the Live Update.
  */
 
 #define pr_fmt(fmt) "PCI: liveupdate: " fmt
@@ -720,6 +724,20 @@ bool pci_liveupdate_inherit_acs(struct pci_dev *dev)
 	return true;
 }
 
+bool pci_liveupdate_inherit_ari(struct pci_dev *dev)
+{
+	u16 val;
+
+	guard(read_lock)(&dev->liveupdate.lock);
+
+	if (!dev->liveupdate.incoming)
+		return false;
+
+	pcie_capability_read_word(dev, PCI_EXP_DEVCTL2, &val);
+	dev->ari_enabled = !!(val & PCI_EXP_DEVCTL2_ARI);
+	return true;
+}
+
 /**
  * pci_liveupdate_is_incoming() - Check if a device is incoming preserved
  * @dev: The PCI device to check
diff --git a/drivers/pci/liveupdate.h b/drivers/pci/liveupdate.h
index c0826ca717e3..fd7693c7ddd2 100644
--- a/drivers/pci/liveupdate.h
+++ b/drivers/pci/liveupdate.h
@@ -16,6 +16,7 @@ void pci_liveupdate_cleanup_device(struct pci_dev *dev);
 bool pci_liveupdate_inherit_buses(void);
 void pci_liveupdate_init_acs(struct pci_dev *dev);
 bool pci_liveupdate_inherit_acs(struct pci_dev *dev);
+bool pci_liveupdate_inherit_ari(struct pci_dev *dev);
 #else
 static inline void pci_liveupdate_setup_device(struct pci_dev *dev)
 {
@@ -38,6 +39,11 @@ static inline bool pci_liveupdate_inherit_acs(struct pci_dev *dev)
 {
 	return false;
 }
+
+static inline bool pci_liveupdate_inherit_ari(struct pci_dev *dev)
+{
+	return false;
+}
 #endif
 
 #endif /* DRIVERS_PCI_LIVEUPDATE_H */
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index cd2c1f2ada92..7e9768dfe092 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3495,7 +3495,7 @@ void pci_configure_ari(struct pci_dev *dev)
 	u32 cap;
 	struct pci_dev *bridge;
 
-	if (pcie_ari_disabled || !pci_is_pcie(dev) || dev->devfn)
+	if (!pci_is_pcie(dev) || dev->devfn)
 		return;
 
 	bridge = dev->bus->self;
@@ -3506,6 +3506,12 @@ void pci_configure_ari(struct pci_dev *dev)
 	if (!(cap & PCI_EXP_DEVCAP2_ARI))
 		return;
 
+	if (pci_liveupdate_inherit_ari(bridge))
+		return;
+
+	if (pcie_ari_disabled)
+		return;
+
 	if (pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ARI)) {
 		pcie_capability_set_word(bridge, PCI_EXP_DEVCTL2,
 					 PCI_EXP_DEVCTL2_ARI);
-- 
2.54.0.563.g4f69b47b94-goog