36506448d4
Reflect three changes: * Virtio now works with Linux and QEMU vhost targets * The Virtio library was separated from bdev modules * Virtio Blk bdev module has been added Change-Id: I7d3075ca863a1142b3ddcc4d18e982f3b7c72202 Signed-off-by: Dariusz Stojaczyk <dariuszx.stojaczyk@intel.com> Reviewed-on: https://review.gerrithub.io/405288 Tested-by: SPDK Automated Test System <sys_sgsw@intel.com> Reviewed-by: Pawel Wodkowski <pawelx.wodkowski@intel.com> Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com> Reviewed-by: Jim Harris <james.r.harris@intel.com>
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Virtio driver
Introduction
SPDK Virtio driver is a C library that allows communicating with Virtio devices. It allows any SPDK application to become an initiator for (SPDK) vhost targets.
The driver supports two different usage models:
- PCI - This is the standard mode of operation when used in a guest virtual machine, where QEMU has presented the virtio controller as a virtual PCI device.
- vhost-user - Can be used to connect to a vhost socket directly on the same host.
The driver, just like the SPDK @ref vhost, is using pollers instead of standard interrupts to check for an I/O response. If used inside a VM, it bypasses interrupt and context switching overhead of QEMU and guest kernel, significantly boosting the overall I/O performance.
This Virtio library is currently used to implement two bdev modules: @ref bdev_config_virtio_scsi and Virtio Blk. These modules will export generic SPDK block devices usable by any other SPDK application.
Limitations
Current Virtio-SCSI implementation has a couple of limitations:
- supports only up to 8 hugepages (implies only 1GB sized pages are practical)
- single LUN per target