From d79c32bd2a17e206d1c198570ef705549d0f644b Mon Sep 17 00:00:00 2001 From: Mark Weiman Date: Sun, 12 Aug 2018 11:36:21 -0400 Subject: [PATCH] PCI: Enable overrides for missing ACS capabilities This an updated version of Alex Williamson's patch from: https://lkml.org/lkml/2013/5/30/513 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. Rebased-by: Alexandre Frade Signed-off-by: Mark Weiman Signed-off-by: Alexandre Frade --- .../admin-guide/kernel-parameters.txt | 9 ++ drivers/pci/quirks.c | 102 ++++++++++++++++++ 2 files changed, 111 insertions(+) --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4475,6 +4475,15 @@ 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. + pcie_acs_override = + [PCIE] Override missing PCIe ACS support for: + downstream + All downstream ports - full ACS capabilities + multifunction + All multifunction devices - multifunction ACS subset + id:nnnn:nnnn + Specific device - full ACS capabilities + Specified as vid:did (vendor/device ID) in hex noioapicquirk [APIC] Disable all boot interrupt quirks. Safety option to keep boot IRQs enabled. This should never be necessary. --- a/drivers/pci/quirks.c +++ b/drivers/pci/quirks.c @@ -3747,6 +3747,106 @@ static void quirk_no_bus_reset(struct pc dev->dev_flags |= PCI_DEV_FLAGS_NO_BUS_RESET; } +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; +} /* * Some NVIDIA GPU devices do not work with bus reset, SBR needs to be * prevented for those affected devices. @@ -5168,6 +5268,8 @@ static const struct pci_dev_acs_enabled { PCI_VENDOR_ID_ZHAOXIN, PCI_ANY_ID, pci_quirk_zhaoxin_pcie_ports_acs }, /* Wangxun nics */ { PCI_VENDOR_ID_WANGXUN, PCI_ANY_ID, pci_quirk_wangxun_nic_acs }, + /* ACS override */ + { PCI_ANY_ID, PCI_ANY_ID, pcie_acs_overrides }, { 0 } };