Bump. Comments? On Thu, 2013-05-30 at 12:40 -0600, Alex Williamson wrote: > 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: Alex Williamson <[email protected]> > --- > Documentation/kernel-parameters.txt | 10 +++ > drivers/pci/quirks.c | 102 > +++++++++++++++++++++++++++++++++++ > 2 files changed, 112 insertions(+) > > diff --git a/Documentation/kernel-parameters.txt > b/Documentation/kernel-parameters.txt > index 47bb23c..a60e6ad 100644 > --- a/Documentation/kernel-parameters.txt > +++ b/Documentation/kernel-parameters.txt > @@ -2349,6 +2349,16 @@ bytes respectively. Such letter suffixes can also be > entirely omitted. > 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. [PARIDE] > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c > index 0369fb6..c7609f6 100644 > --- a/drivers/pci/quirks.c > +++ b/drivers/pci/quirks.c > @@ -3292,11 +3292,113 @@ struct pci_dev *pci_get_dma_source(struct pci_dev > *dev) > 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; > +} > + > static const struct pci_dev_acs_enabled { > u16 vendor; > u16 device; > int (*acs_enabled)(struct pci_dev *dev, u16 acs_flags); > } pci_dev_acs_enabled[] = { > + { PCI_ANY_ID, PCI_ANY_ID, pcie_acs_overrides }, > { 0 } > }; > >
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