This patch is an attempt to resolve an issue which can occur when using vfio-pci (and vfio-platform) with IOMMU direct assignment. When attempting to directly assign a device to a virtual machine, the normal flow is something like the following: echo <pci address> > /sys/bus/pci/drivers/<old driver>/unbind echo <device id> > /sys/bus/pci/drivers/vfio-pci/new_id echo <pci address> > /sys/bus/pci/drivers/vfio-pci/bind This process results in the device being bound to the vfio-pci stub driver, and then this device can be safely given to a virtual machine. The issue can occur, that if <device id> doesn't currently have a driver loaded, (like say the module was removed), the process of adding <new_id> can result in *all* devices which match that id being bound to vfio-pci. This may not seem like a problem, but it can be confusing when you have a dual-port device, such as a networking card. In some use cases, you only want to assign a single port to a VM and not all the ports. If you happen to not have the driver loaded already, the result is that even loading the driver later will not gain control of the 2nd port, because the device is already bound to vfio-pci. The solution (if you know this is the case) would be to unbind that particular device from vfio and bind it to the real driver. This patch fixes the issue by instead requiring vfio-pci and vfio-platform to only bind to devices given via the sysfs bind route, and prevents bind to any devices in other scenarios. The result is that vfio-pci will never bind a device unless explicitly requested. Given the nature of what vfio-pci does, I think this is a much better solution. I've tried to Cc several people who've made changes to this area of th kernel for more feedback. Jacob Keller (1): driver: add manual_bind_only option for virtual stub drivers drivers/base/dd.c | 6 ++++++ drivers/vfio/pci/vfio_pci.c | 3 +++ drivers/vfio/platform/vfio_platform.c | 1 + include/linux/device.h | 1 + 4 files changed, 11 insertions(+) -- 2.6.3.505.g5cc1fd1 -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
