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>
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 6af212c..cd9b375 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1550,6 +1550,16 @@
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 @@
u16 cap;
u16 ctrl;
+ if (!pci_acs_enable)
+ return;
+
if (!pci_is_pcie(dev))
return;