[libvirt] [question]Why libvirt bind all devices with same vendor id and device id to vfio-pci driver, and only unbind devices used by VMs to original driver?
Hi, As the title says, I thought that it's a bit unreasonable and inconsistent to unbind devices assigned to VMs to original driver and leave other devices binding to vfio-pci driver. Why not to bind devices we need to vfio-pci driver instead of bind all devices with same type to vfio-pci driver? Or, we may can rebind devices unused with same type to original driver. Thanks, Zongyong Wu
On Mon, 9 Oct 2017 09:28:27 +0000 "Wuzongyong (Euler Dept)" <cordius.wu@huawei.com> wrote:
Hi,
As the title says, I thought that it's a bit unreasonable and inconsistent to unbind devices assigned to VMs to original driver and leave other devices binding to vfio-pci driver. Why not to bind devices we need to vfio-pci driver instead of bind all devices with same type to vfio-pci driver? Or, we may can rebind devices unused with same type to original driver.
Because that's the way the kernel's new_id interface works, any matching device without a driver will probe the new_id driver. For a new enough kernel and libvirt, the driver_override interface should be used instead, which will only bind the target device. Thanks, Alex
On 10/09/2017 10:57 AM, Alex Williamson wrote:
On Mon, 9 Oct 2017 09:28:27 +0000 "Wuzongyong (Euler Dept)" <cordius.wu@huawei.com> wrote:
Hi,
As the title says, I thought that it's a bit unreasonable and inconsistent to unbind devices assigned to VMs to original driver and leave other devices binding to vfio-pci driver. Why not to bind devices we need to vfio-pci driver instead of bind all devices with same type to vfio-pci driver? Or, we may can rebind devices unused with same type to original driver.
Because that's the way the kernel's new_id interface works, any matching device without a driver will probe the new_id driver. For a new enough kernel and libvirt, the driver_override interface should be used instead, which will only bind the target device.
Note that all libvirt 2.3.0 and later uses driver_override rather than new_id (as long as the host kernel also supports it, which these days should almost always be the case). If you're seeing *all* unbound devices being bound to vfio-pci when only one of the devices is assigned to a guest, then either 1) you are using a host with a *very* old kernel, 2) you have modified libvirt's code to somehow force taking the old/deprecated path, or 3) there is a bug in libvirt's code.
participants (3)
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Alex Williamson -
Laine Stump -
Wuzongyong (Euler Dept)