[PATCH 4/4] PCI: document SR-IOV
SR-IOV Documentation.
Signed-off-by: Yu Zhao <yu.zhao@xxxxxxxxx>
Signed-off-by: Eddie Dong <eddie.dong@xxxxxxxxx>
---
Documentation/ABI/testing/sysfs-bus-pci | 13 ++
Documentation/PCI/00-INDEX | 2
Documentation/PCI/pci-iov-howto.txt | 170 +++++++++++++++++++++++++++++++
3 files changed, 185 insertions(+), 0 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-bus-pci
b/Documentation/ABI/testing/sysfs-bus-pci
index ceddcff..9ada27b 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci
+++ b/Documentation/ABI/testing/sysfs-bus-pci
@@ -9,3 +9,16 @@ Description:
that some devices may have malformatted data. If the
underlying VPD has a writable section then the
corresponding section of this file will be writable.
+
+What: /sys/bus/pci/devices/.../iov
+Date: August 2008
+Contact: Yu Zhao <yu.zhao@xxxxxxxxx>
+Description:
+ This file will appear when SR-IOV capability is enabled
+ by the device driver if supported. It holds number of
+ available Virtual Functions and Bus, Device, Function
+ number and status of these Virtual Functions that belong
+ to this device (Physical Function). This file can be
+ written using same format as what can be read out, to
+ change the number of available Virtual Functions and to
+ enable or disable a Virtual Functions.
diff --git a/Documentation/PCI/00-INDEX b/Documentation/PCI/00-INDEX
index 49f4394..8f8ee17 100644
--- a/Documentation/PCI/00-INDEX
+++ b/Documentation/PCI/00-INDEX
@@ -10,3 +10,5 @@ pci.txt
- info on the PCI subsystem for device driver authors
pcieaer-howto.txt
- the PCI Express Advanced Error Reporting Driver Guide HOWTO
+pci-iov-howto.txt
+ - PCI Express Single Root I/O Virtualization HOWTO
diff --git a/Documentation/PCI/pci-iov-howto.txt
b/Documentation/PCI/pci-iov-howto.txt
new file mode 100644
index 0000000..2d7ae64
--- /dev/null
+++ b/Documentation/PCI/pci-iov-howto.txt
@@ -0,0 +1,170 @@
+ PCI Express Single Root I/O Virtualization HOWTO
+ Copyright (C) 2008 Intel Corporation
+ Yu Zhao <yu.zhao@xxxxxxxxx>
+
+
+1. Overview
+
+1.1 What is SR-IOV
+
+SR-IOV is PCI Express Extended Capability, which makes one physical device
+becomes multiple virtual devices. The physical device is referred as Physical
+Function while the virtual devices are refereed as Virtual Functions.
+Allocation of Virtual Functions can be dynamically controlled by Physical
+Function via registers encapsulated in the capability. By default, this
+feature is not enabled and the Physical Function behaves as traditional PCIe
+device. Once it's turned on, each Virtual Function's PCI configuration space
+can be accessed by its own Bus, Device and Function Number (Routing ID). And
+each Virtual Function also has PCI Memory Space, which is used to map its
+register set. Virtual Function device driver operates on the register set so
+it can be functional and appear as a real existing PCI device.
+
+1.2 What is ARI
+
+Alternative Routing-ID Interpretation allows a PCI Express Endpoint to use
+its device number field as part of function number. Traditionally, an
+Endpoint can only have 8 functions, and the device number of all Endpoints
+is zero. With ARI enabled, an Endpoint can have up to 256 functions. ARI is
+managed via a ARI Forwarding bit in the Device Capabilities 2 register of
+the PCI Express Capability on the Root Port or the Downstream Port and a new
+ARI Capability on the Endpoint.
+
+
+2. User Guide
+
+2.1 How can I manage SR-IOV
+
+SR-IOV can be managed by reading or writing /sys/bus/pci/devices/.../iov.
+Legal operations on this file include:
+ - Read: will get number of available VFs and a list of them.
+ - Write: bb:dd.f={1|0} will enable or disable a VF.
+ - Write: NumVFs=N will change number of available VFs.
+
+2.2 How can I use Virtual Functions
+
+Virtual Functions can be treated as hot-plugged PCI devices in the kernel,
+so they should be able to work in the same way as real PCI devices.
+NOTE: Virtual Function device driver must be loaded to make it work.
+
+
+3. Developer Guide
+
+3.1 SR-IOV APIs
+
+To enable SR-IOV, Physical Function device driver needs to call:
+ int pci_iov_enable(struct pci_dev *dev, int nvfs,
+ int (*cb)(struct pci_dev *, int, int))
+NOTE: this function sleeps 2 seconds waiting on hardware transaction
+completion according to SR-IOV specification.
+
+To disable SR-IOV, Physical Function device driver needs to call:
+ void pci_iov_disable(struct pci_dev *dev)
+NOTE: this function sleeps 1 second waiting on hardware transaction
+completion according to SR-IOV specification.
+
+Following function can be used to query maximum number of Virtual Functions
+that a Physical Function can support:
+ int pci_iov_max_virtfn(struct pci_dev *dev)
+
+Following function can be used to retrieve parameter of a Virtual Function:
+ const char *pci_iov_virtfn_param(struct pci_dev *dev, int vfid)
+
+3.2 Usage example
+
+Following piece of codes illustrates the usage of APIs above.
+
+static int callback(struct pci_dev *dev, int event, int arg)
+{
+ int err;
+ const char *param;
+
+ switch (event) {
+ case PCI_IOV_VF_ENA: /* request to enable a VF */
+ param = pci_iov_virtfn_param(dev, arg);
+ ...
+ break;
+ case PCI_IOV_VF_DIS: /* a VF is disabled */
+ /*
+ * reclaim hardware resource if needed
+ */
+ break;
+ case PCI_IOV_VF_PAR: /* VF parameter changed */
+ param = pci_iov_virtfn_param(dev, arg);
+ ...
+ break;
+ case PCI_IOV_VF_NUM: /* request to change NumVFs */
+ /*
+ * adjust hardware resources if needed
+ * NOTE: arg is the new requested NumVFs
+ */
+ break;
+ case PCI_IOV_VF_ERR: /* error occurred */
+ /*
+ * error handling
+ * NOTE: arg is the error code
+ */
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ return err;
+}
+
+static int __devinit dev_probe(struct pci_dev *dev,
+ const struct pci_device_id *id)
+{
+ int err, nvfs;
+
+ ...
+
+ nvfs = pci_iov_max_virtfn(dev);
+ if (nvfs <= 0)
+ return -ENODEV;
+
+ err = pci_iov_enable(dev, nvfs, callback);
+ if (err)
+ return err;
+
+ ...
+}
+
+static void __devexit dev_remove(struct pci_dev *dev)
+{
+ ...
+
+ pci_iov_disable(dev);
+
+ ...
+}
+
+#ifdef CONFIG_PM
+static int dev_suspend(struct pci_dev *dev, pm_message_t state)
+{
+ ...
+
+ pci_iov_disable(dev);
+
+ ...
+}
+
+static int dev_resume(struct pci_dev *dev)
+{
+ ...
+
+ pci_iov_enable(dev, nvfs, callback);
+
+ ...
+}
+#endif
+
+static struct pci_driver dev_driver = {
+ .name = "SR-IOV PF driver",
+ .id_table = dev_id_table,
+ .probe = dev_probe,
+ .remove = __devexit_p(dev_remove),
+#ifdef CONFIG_PM
+ .suspend = dev_suspend,
+ .resume = dev_resume,
+#endif
+};
--
1.4.2.1
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