3 files changed, 42 insertions, 0 deletions

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 4859669f0ab5..557218222826 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1546,6 +1546,41 @@ void pci_enable_ari(struct pci_dev *dev)
 }
 
 /**
+ * pci_enable_acs - enable ACS if hardware support it
+ * @dev: the PCI device
+ */
+void pci_enable_acs(struct pci_dev *dev)
+{
+        int pos;
+        u16 cap;
+        u16 ctrl;
+
+        if (!dev->is_pcie)
+                return;
+
+        pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ACS);
+        if (!pos)
+                return;
+
+        pci_read_config_word(dev, pos + PCI_ACS_CAP, &cap);
+        pci_read_config_word(dev, pos + PCI_ACS_CTRL, &ctrl);
+
+        /* Source Validation */
+        ctrl |= (cap & PCI_ACS_SV);
+
+        /* P2P Request Redirect */
+        ctrl |= (cap & PCI_ACS_RR);
+
+        /* P2P Completion Redirect */
+        ctrl |= (cap & PCI_ACS_CR);
+
+        /* Upstream Forwarding */
+        ctrl |= (cap & PCI_ACS_UF);
+
+        pci_write_config_word(dev, pos + PCI_ACS_CTRL, ctrl);
+}
+
+/**
  * pci_swizzle_interrupt_pin - swizzle INTx for device behind bridge
  * @dev: the PCI device
  * @pin: the INTx pin (1=INTA, 2=INTB, 3=INTD, 4=INTD)
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index d92d1954a2fb..33ed8e0aba1e 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -311,4 +311,6 @@ static inline int pci_resource_alignment(struct pci_dev *dev,
         return resource_alignment(res);
 }
 
+extern void pci_enable_acs(struct pci_dev *dev);
+
 #endif /* DRIVERS_PCI_H */
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 2adb47574d86..aac5b156a5c5 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -10,6 +10,7 @@
 #include <linux/module.h>
 #include <linux/cpumask.h>
 #include <linux/pci-aspm.h>
+#include <linux/iommu.h>
 #include "pci.h"
 
 #define CARDBUS_LATENCY_TIMER   176     /* secondary latency timer */
@@ -1004,6 +1005,10 @@ static void pci_init_capabilities(struct pci_dev *dev)
 
         /* Single Root I/O Virtualization */
         pci_iov_init(dev);
+
+        /* Enable ACS P2P upstream forwarding */
+        if (iommu_found())
+                pci_enable_acs(dev);
 }
 
 void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)