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, 5 insertions, 0 deletions

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 5bccd706232c..e2511bccbc8d 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -27,6 +27,7 @@
 #include <linux/page-flags.h>
 #include <linux/highmem.h>
 #include <linux/console.h>
+#include <linux/pci.h>
 
 #include <xen/xen.h>
 #include <xen/interface/xen.h>
@@ -1170,7 +1171,11 @@ asmlinkage void __init xen_start_kernel(void)
                 add_preferred_console("xenboot", 0, NULL);
                 add_preferred_console("tty", 0, NULL);
                 add_preferred_console("hvc", 0, NULL);
+        } else {
+                /* Make sure ACS will be enabled */
+                pci_request_acs();
         }
+                
 
         xen_raw_console_write("about to get started...\n");