diff -rupN linux-3.15.old/Documentation/kernel-parameters.txt linux-3.15/Documentation/kernel-parameters.txt
--- linux-3.15.old/Documentation/kernel-parameters.txt	2014-06-08 15:19:54.000000000 -0300
+++ linux-3.15/Documentation/kernel-parameters.txt	2014-06-09 18:05:31.744055580 -0300
@@ -2554,6 +2554,16 @@ bytes respectively. Such letter suffixes
 		nomsi	Do not use MSI for native PCIe PME signaling (this makes
 			all PCIe root ports use INTx for all services).
 
+	pcie_acs_override =
+			[PCIE] Override missing PCIe ACS support for:
+		downstream
+			All downstream ports - full ACS capabilties
+		multifunction
+			All multifunction devices - multifunction ACS subset
+		id:nnnn:nnnn
+			Specfic device - full ACS capabilities
+			Specified as vid:did (vendor/device ID) in hex
+
 	pcmv=		[HW,PCMCIA] BadgePAD 4
 
 	pd_ignore_unused
diff -rupN linux-3.15.old/drivers/pci/quirks.c linux-3.15/drivers/pci/quirks.c
--- linux-3.15.old/drivers/pci/quirks.c	2014-06-08 15:19:54.000000000 -0300
+++ linux-3.15/drivers/pci/quirks.c	2014-06-09 18:06:36.688743183 -0300
@@ -3384,6 +3384,107 @@ struct pci_dev *pci_get_dma_source(struc
 	return pci_dev_get(dev);
 }
 
+static bool acs_on_downstream;
+static bool acs_on_multifunction;
+
+#define NUM_ACS_IDS 16
+struct acs_on_id {
+	unsigned short vendor;
+	unsigned short device;
+};
+static struct acs_on_id acs_on_ids[NUM_ACS_IDS];
+static u8 max_acs_id;
+
+static __init int pcie_acs_override_setup(char *p)
+{
+	if (!p)
+		return -EINVAL;
+
+	while (*p) {
+		if (!strncmp(p, "downstream", 10))
+			acs_on_downstream = true;
+		if (!strncmp(p, "multifunction", 13))
+			acs_on_multifunction = true;
+		if (!strncmp(p, "id:", 3)) {
+			char opt[5];
+			int ret;
+			long val;
+
+			if (max_acs_id >= NUM_ACS_IDS - 1) {
+				pr_warn("Out of PCIe ACS override slots (%d)\n",
+					NUM_ACS_IDS);
+				goto next;
+			}
+
+			p += 3;
+			snprintf(opt, 5, "%s", p);
+			ret = kstrtol(opt, 16, &val);
+			if (ret) {
+				pr_warn("PCIe ACS ID parse error %d\n", ret);
+				goto next;
+			}
+			acs_on_ids[max_acs_id].vendor = val;
+
+			p += strcspn(p, ":");
+			if (*p != ':') {
+				pr_warn("PCIe ACS invalid ID\n");
+				goto next;
+			}
+
+			p++;
+			snprintf(opt, 5, "%s", p);
+			ret = kstrtol(opt, 16, &val);
+			if (ret) {
+				pr_warn("PCIe ACS ID parse error %d\n", ret);
+				goto next;
+			}
+			acs_on_ids[max_acs_id].device = val;
+			max_acs_id++;
+		}
+next:
+		p += strcspn(p, ",");
+		if (*p == ',')
+			p++;
+	}
+
+	if (acs_on_downstream || acs_on_multifunction || max_acs_id)
+		pr_warn("Warning: PCIe ACS overrides enabled; This may allow non-IOMMU protected peer-to-peer DMA\n");
+
+	return 0;
+}
+early_param("pcie_acs_override", pcie_acs_override_setup);
+
+static int pcie_acs_overrides(struct pci_dev *dev, u16 acs_flags)
+{
+	int i;
+
+	/* Never override ACS for legacy devices or devices with ACS caps */
+	if (!pci_is_pcie(dev) ||
+	    pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ACS))
+		return -ENOTTY;
+
+	for (i = 0; i < max_acs_id; i++)
+		if (acs_on_ids[i].vendor == dev->vendor &&
+		    acs_on_ids[i].device == dev->device)
+			return 1;
+
+	switch (pci_pcie_type(dev)) {
+	case PCI_EXP_TYPE_DOWNSTREAM:
+	case PCI_EXP_TYPE_ROOT_PORT:
+		if (acs_on_downstream)
+			return 1;
+		break;
+	case PCI_EXP_TYPE_ENDPOINT:
+	case PCI_EXP_TYPE_UPSTREAM:
+	case PCI_EXP_TYPE_LEG_END:
+	case PCI_EXP_TYPE_RC_END:
+		if (acs_on_multifunction && dev->multifunction)
+			return 1;
+	}
+
+	return -ENOTTY;
+}
+
 /*
  * AMD has indicated that the devices below do not support peer-to-peer
  * in any system where they are found in the southbridge with an AMD
@@ -3483,6 +3584,7 @@ static int pci_quirk_intel_pch_acs(struc
 	return acs_flags & ~flags ? 0 : 1;
 }
 
+
 static const struct pci_dev_acs_enabled {
 	u16 vendor;
 	u16 device;
@@ -3495,6 +3597,7 @@ static const struct pci_dev_acs_enabled
 	{ PCI_VENDOR_ID_ATI, 0x4384, pci_quirk_amd_sb_acs },
 	{ PCI_VENDOR_ID_ATI, 0x4399, pci_quirk_amd_sb_acs },
 	{ PCI_VENDOR_ID_INTEL, PCI_ANY_ID, pci_quirk_intel_pch_acs },
+	{ PCI_ANY_ID, PCI_ANY_ID, pcie_acs_overrides },
 	{ 0 }
 };