100 lines
2.5 KiB
Text
100 lines
2.5 KiB
Text
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PCI Express I/O Virtualization Howto
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Copyright (C) 2009 Intel Corporation
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Yu Zhao <yu.zhao@intel.com>
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1. Overview
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1.1 What is SR-IOV
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Single Root I/O Virtualization (SR-IOV) is a PCI Express Extended
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capability which makes one physical device appear as multiple virtual
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devices. The physical device is referred to as Physical Function (PF)
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while the virtual devices are referred to as Virtual Functions (VF).
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Allocation of the VF can be dynamically controlled by the PF via
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registers encapsulated in the capability. By default, this feature is
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not enabled and the PF behaves as traditional PCIe device. Once it's
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turned on, each VF's PCI configuration space can be accessed by its own
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Bus, Device and Function Number (Routing ID). And each VF also has PCI
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Memory Space, which is used to map its register set. VF device driver
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operates on the register set so it can be functional and appear as a
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real existing PCI device.
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2. User Guide
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2.1 How can I enable SR-IOV capability
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The device driver (PF driver) will control the enabling and disabling
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of the capability via API provided by SR-IOV core. If the hardware
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has SR-IOV capability, loading its PF driver would enable it and all
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VFs associated with the PF.
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2.2 How can I use the Virtual Functions
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The VF is treated as hot-plugged PCI devices in the kernel, so they
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should be able to work in the same way as real PCI devices. The VF
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requires device driver that is same as a normal PCI device's.
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3. Developer Guide
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3.1 SR-IOV API
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To enable SR-IOV capability:
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int pci_enable_sriov(struct pci_dev *dev, int nr_virtfn);
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'nr_virtfn' is number of VFs to be enabled.
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To disable SR-IOV capability:
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void pci_disable_sriov(struct pci_dev *dev);
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To notify SR-IOV core of Virtual Function Migration:
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irqreturn_t pci_sriov_migration(struct pci_dev *dev);
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3.2 Usage example
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Following piece of code illustrates the usage of the SR-IOV API.
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static int __devinit dev_probe(struct pci_dev *dev, const struct pci_device_id *id)
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{
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pci_enable_sriov(dev, NR_VIRTFN);
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...
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return 0;
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}
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static void __devexit dev_remove(struct pci_dev *dev)
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{
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pci_disable_sriov(dev);
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...
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}
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static int dev_suspend(struct pci_dev *dev, pm_message_t state)
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{
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...
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return 0;
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}
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static int dev_resume(struct pci_dev *dev)
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{
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...
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return 0;
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}
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static void dev_shutdown(struct pci_dev *dev)
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{
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...
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}
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static struct pci_driver dev_driver = {
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.name = "SR-IOV Physical Function driver",
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.id_table = dev_id_table,
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.probe = dev_probe,
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.remove = __devexit_p(dev_remove),
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.suspend = dev_suspend,
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.resume = dev_resume,
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.shutdown = dev_shutdown,
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};
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