PCI: add pci_request_acs

Commit ae21ee65e8bc228416bbcc8a1da01c56a847a60c "PCI: acs p2p upsteram
forwarding enabling" doesn't actually enable ACS.

Add a function to pci core to allow an IOMMU to request that ACS
be enabled.  The existing mechanism of using iommu_found() in the pci
core to know when ACS should be enabled doesn't actually work due to
initialization order;  iommu has only been detected not initialized.

Have Intel and AMD IOMMUs request ACS, and Xen does as well during early
init of dom0.

Cc: Allen Kay <allen.m.kay@intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

3 files changed, 18 insertions, 5 deletions

diff --git a/drivers/pci/dmar.c b/drivers/pci/dmar.c
index e01ca4d6b3e6..0e98f6b6f515 100644
--- a/drivers/pci/dmar.c
+++ b/drivers/pci/dmar.c
@@ -614,8 +614,11 @@ void __init detect_intel_iommu(void)
 #endif
 #ifdef CONFIG_DMAR
                 if (ret && !no_iommu && !iommu_detected && !swiotlb &&
-                    !dmar_disabled)
+                    !dmar_disabled) {
                         iommu_detected = 1;
+                        /* Make sure ACS will be enabled */
+                        pci_request_acs();
+                }
 #endif
         }
         early_acpi_os_unmap_memory(dmar_tbl, dmar_tbl_size);
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 6af212c509c5..cd9b375f49d5 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1550,6 +1550,16 @@ void pci_enable_ari(struct pci_dev *dev)
         bridge->ari_enabled = 1;
 }
 
+static int pci_acs_enable;
+
+/**
+ * pci_request_acs - ask for ACS to be enabled if supported
+ */
+void pci_request_acs(void)
+{
+        pci_acs_enable = 1;
+}
+
 /**
  * pci_enable_acs - enable ACS if hardware support it
  * @dev: the PCI device
@@ -1560,6 +1570,9 @@ void pci_enable_acs(struct pci_dev *dev)
         u16 cap;
         u16 ctrl;
 
+        if (!pci_acs_enable)
+                return;
+
         if (!pci_is_pcie(dev))
                 return;
 
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 2fdffc02a308..98ffb2de22e9 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -10,9 +10,7 @@
 #include <linux/module.h>
 #include <linux/cpumask.h>
 #include <linux/pci-aspm.h>
-#include <linux/iommu.h>
 #include <acpi/acpi_hest.h>
-#include <xen/xen.h>
 #include "pci.h"
 
 #define CARDBUS_LATENCY_TIMER   176     /* secondary latency timer */
@@ -1029,8 +1027,7 @@ static void pci_init_capabilities(struct pci_dev *dev)
         pci_iov_init(dev);
 
         /* Enable ACS P2P upstream forwarding */
-        if (iommu_found() || xen_initial_domain())
-                pci_enable_acs(dev);
+        pci_enable_acs(dev);
 }
 
 void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)