PCIe spec 5.0 r1.0 section 2.2.6.2 says that if an Endpoint supports sending Requests to other Endpoints (as opposed to host memory), the Endpoint must not send 10-Bit Tag Requests to another given Endpoint unless an implementation-specific mechanism determines that the Endpoint supports 10-Bit Tag Completer capability. Add a 10bit_tag sysfs file, write 0 to disable 10-Bit Tag Requester when the driver does not bind the device if the peer device does not support the 10-Bit Tag Completer. This will make P2P traffic safe. the 10bit_tag file content indicate current 10-Bit Tag Requester Enable status. Signed-off-by: Dongdong Liu <liudongdong3@xxxxxxxxxx> --- Documentation/ABI/testing/sysfs-bus-pci | 16 +++++++- drivers/pci/pci-sysfs.c | 69 +++++++++++++++++++++++++++++++++ 2 files changed, 84 insertions(+), 1 deletion(-) diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci index 793cbb7..0e0c97d 100644 --- a/Documentation/ABI/testing/sysfs-bus-pci +++ b/Documentation/ABI/testing/sysfs-bus-pci @@ -139,7 +139,7 @@ Description: binary file containing the Vital Product Data for the device. It should follow the VPD format defined in PCI Specification 2.1 or 2.2, but users should consider - that some devices may have incorrectly formatted data. + that some devices may have incorrectly formatted data. If the underlying VPD has a writable section then the corresponding section of this file will be writable. @@ -407,3 +407,17 @@ Description: The file is writable if the PF is bound to a driver that implements ->sriov_set_msix_vec_count(). + +What: /sys/bus/pci/devices/.../10bit_tag +Date: August 2021 +Contact: Dongdong Liu <liudongdong3@xxxxxxxxxx> +Description: + If a PCI device support 10-Bit Tag Requester, will create the + 10bit_tag sysfs file. The file is readable, the value + indicate current 10-Bit Tag Requester Enable. + 1 - enabled, 0 - disabled. + + The file is also writeable, the value only accept by write 0 + to disable 10-Bit Tag Requester when the driver does not bind + the deivce. The typical use case is for p2pdma when the peer + device does not support 10-BIT Tag Completer. diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c index 5d63df7..e93ce8b 100644 --- a/drivers/pci/pci-sysfs.c +++ b/drivers/pci/pci-sysfs.c @@ -306,6 +306,49 @@ static ssize_t enable_show(struct device *dev, struct device_attribute *attr, } static DEVICE_ATTR_RW(enable); +static ssize_t pci_10bit_tag_store(struct device *dev, + struct device_attribute *attr, + const char *buf, size_t count) +{ + struct pci_dev *pdev = to_pci_dev(dev); + bool enable; + + if (kstrtobool(buf, &enable) < 0) + return -EINVAL; + + if (enable != false ) + return -EINVAL; + + if (pdev->driver) + return -EBUSY; + + pcie_capability_clear_word(pdev, PCI_EXP_DEVCTL2, + PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN); + pci_info(pdev, "disabled 10-Bit Tag Requester\n"); + + return count; +} + +static ssize_t pci_10bit_tag_show(struct device *dev, + struct device_attribute *attr, + char *buf) +{ + struct pci_dev *pdev = to_pci_dev(dev); + u16 ctl; + int ret; + + ret = pcie_capability_read_word(pdev, PCI_EXP_DEVCTL2, &ctl); + if (ret) + return -EINVAL; + + return sysfs_emit(buf, "%u\n", + !!(ctl & PCI_EXP_DEVCTL2_10BIT_TAG_REQ_EN)); +} + +static struct device_attribute dev_attr_10bit_tag = __ATTR(10bit_tag, 0600, + pci_10bit_tag_show, + pci_10bit_tag_store); + #ifdef CONFIG_NUMA static ssize_t numa_node_store(struct device *dev, struct device_attribute *attr, const char *buf, @@ -635,6 +678,11 @@ static struct attribute *pcie_dev_attrs[] = { NULL, }; +static struct attribute *pcie_dev_10bit_tag_attrs[] = { + &dev_attr_10bit_tag.attr, + NULL, +}; + static struct attribute *pcibus_attrs[] = { &dev_attr_bus_rescan.attr, &dev_attr_cpuaffinity.attr, @@ -1482,6 +1530,21 @@ static umode_t pcie_dev_attrs_are_visible(struct kobject *kobj, return 0; } +static umode_t pcie_dev_10bit_tag_attrs_are_visible(struct kobject *kobj, + struct attribute *a, int n) +{ + struct device *dev = kobj_to_dev(kobj); + struct pci_dev *pdev = to_pci_dev(dev); + + if (pdev->is_virtfn) + return 0; + + if (!(pdev->pcie_devcap2 & PCI_EXP_DEVCAP2_10BIT_TAG_REQ)) + return 0; + + return a->mode; +} + static const struct attribute_group pci_dev_group = { .attrs = pci_dev_attrs, }; @@ -1521,6 +1584,11 @@ static const struct attribute_group pcie_dev_attr_group = { .is_visible = pcie_dev_attrs_are_visible, }; +static const struct attribute_group pcie_dev_10bit_tag_attr_group = { + .attrs = pcie_dev_10bit_tag_attrs, + .is_visible = pcie_dev_10bit_tag_attrs_are_visible, +}; + static const struct attribute_group *pci_dev_attr_groups[] = { &pci_dev_attr_group, &pci_dev_hp_attr_group, @@ -1530,6 +1598,7 @@ static const struct attribute_group *pci_dev_attr_groups[] = { #endif &pci_bridge_attr_group, &pcie_dev_attr_group, + &pcie_dev_10bit_tag_attr_group, #ifdef CONFIG_PCIEAER &aer_stats_attr_group, #endif -- 2.7.4