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>

1 files changed, 1 insertions, 4 deletions

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)