path: root/add-acs-overrides.patch
diff options
Diffstat (limited to 'add-acs-overrides.patch')
1 files changed, 52 insertions, 13 deletions
diff --git a/add-acs-overrides.patch b/add-acs-overrides.patch
index b92a5f326d6..b4c39f178ed 100644
--- a/add-acs-overrides.patch
+++ b/add-acs-overrides.patch
@@ -1,22 +1,61 @@
-From 087743912610c92eeff1ffbfbd2964faac969d0f Mon Sep 17 00:00:00 2001
+From 3cf550fd8ca366897abe643442d198d1647cadc7 Mon Sep 17 00:00:00 2001
From: Mark Weiman <>
-Date: Sun, 24 Jun 2018 12:31:25 -0400
-Subject: [PATCH] pci: Enable overrides for missing ACS capabilities (4.17)
+Date: Sun, 12 Aug 2018 11:36:21 -0400
+Subject: [PATCH] pci: Enable overrides for missing ACS capabilities (4.17.14)
This an updated version of Alex Williamson's patch from:
Original commit message follows:
+PCIe ACS (Access Control Services) is the PCIe 2.0+ feature that
+allows us to control whether transactions are allowed to be redirected
+in various subnodes of a PCIe topology. For instance, if two
+endpoints are below a root port or downsteam switch port, the
+downstream port may optionally redirect transactions between the
+devices, bypassing upstream devices. The same can happen internally
+on multifunction devices. The transaction may never be visible to the
+upstream devices.
+One upstream device that we particularly care about is the IOMMU. If
+a redirection occurs in the topology below the IOMMU, then the IOMMU
+cannot provide isolation between devices. This is why the PCIe spec
+encourages topologies to include ACS support. Without it, we have to
+assume peer-to-peer DMA within a hierarchy can bypass IOMMU isolation.
+Unfortunately, far too many topologies do not support ACS to make this
+a steadfast requirement. Even the latest chipsets from Intel are only
+sporadically supporting ACS. We have trouble getting interconnect
+vendors to include the PCIe spec required PCIe capability, let alone
+suggested features.
+Therefore, we need to add some flexibility. The pcie_acs_override=
+boot option lets users opt-in specific devices or sets of devices to
+assume ACS support. The "downstream" option assumes full ACS support
+on root ports and downstream switch ports. The "multifunction"
+option assumes the subset of ACS features available on multifunction
+endpoints and upstream switch ports are supported. The "id:nnnn:nnnn"
+option enables ACS support on devices matching the provided vendor
+and device IDs, allowing more strategic ACS overrides. These options
+may be combined in any order. A maximum of 16 id specific overrides
+are available. It's suggested to use the most limited set of options
+necessary to avoid completely disabling ACS across the topology.
+Note to hardware vendors, we have facilities to permanently quirk
+specific devices which enforce isolation but not provide an ACS
+capability. Please contact me to have your devices added and save
+your customers the hassle of this boot option.
+Signed-off-by: Mark Weiman <>
.../admin-guide/kernel-parameters.txt | 8 ++
drivers/pci/quirks.c | 102 ++++++++++++++++++
2 files changed, 110 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
-index 533ff5c68970..353481231683 100644
+index ff4ba249a26f..e23d259d461f 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
-@@ -3028,6 +3028,14 @@
+@@ -3019,6 +3019,14 @@
nomsi [MSI] If the PCI_MSI kernel config parameter is
enabled, this kernel boot option can be used to
disable the use of MSI interrupts system-wide.
@@ -32,11 +71,11 @@ index 533ff5c68970..353481231683 100644
Safety option to keep boot IRQs enabled. This
should never be necessary.
diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
-index f439de848658..5c3ec5e04349 100644
+index 785a29ba4f51..63fb2096f90d 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
-@@ -186,6 +186,106 @@ static int __init pci_apply_final_quirks(void)
- }
+@@ -3533,6 +3533,106 @@ static int __init pci_apply_final_quirks(void)
+static bool acs_on_downstream;
@@ -140,14 +179,14 @@ index f439de848658..5c3ec5e04349 100644
- * Decoding should be disabled for a PCI device during BAR sizing to avoid
- * conflict. But doing so may cause problems on host bridge and perhaps other
-@@ -4395,6 +4495,8 @@ static const struct pci_dev_acs_enabled {
+ * Following are device-specific reset methods which can be used to
+ * reset a single function if other methods (e.g. FLR, PM D0->D3) are
+@@ -4401,6 +4501,8 @@ static const struct pci_dev_acs_enabled {
{ PCI_VENDOR_ID_AMPERE, 0xE00A, pci_quirk_xgene_acs },
{ PCI_VENDOR_ID_AMPERE, 0xE00B, pci_quirk_xgene_acs },
{ PCI_VENDOR_ID_AMPERE, 0xE00C, pci_quirk_xgene_acs },
-+ /* allow acs for any */
-+ { PCI_ANY_ID, PCI_ANY_ID, pcie_acs_overrides },
++ /* allow acs for any */
++ { PCI_ANY_ID, PCI_ANY_ID, pcie_acs_overrides },
{ 0 }