On 2021/8/5 23:31, Bjorn Helgaas wrote:
On Thu, Aug 05, 2021 at 04:37:39PM +0800, Dongdong Liu wrote:
On 2021/8/5 7:49, Bjorn Helgaas wrote:
On Wed, Aug 04, 2021 at 09:47:06PM +0800, Dongdong Liu wrote:
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.
+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;
Is this the same as "if (enable)"?
Yes, Will fix.
I actually don't like the one-way nature of this. When the hierarchy
supports 10-bit tags, we automatically enable them during enumeration.
Then we provide this sysfs file, but it can only *disable* 10-bit
tags. There's no way to re-enable them except by rebooting (or using
setpci, I guess).
Why can't we allow *enabling* them here if they're supported in this
hierarchy?
Yes, we can also provide this sysfs to enable 10-bit tag for EP devices
when the hierarchy supports 10-bit tags.
I do not want to provide sysfs to enable/disable 10-bit tag for RP
devices as I can not tell current if the the Function has outstanding
Non-Posted Requests, may need to unbind all the EP drivers under the
RP, and current seems no scenario need to do this. This will make things
more complex.
Thanks,
Dongdong
+ 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;
+}
.
