Re: [libvirt PATCH v3 4/8] util: permit existing binding to VFIO variant driver

Before a PCI device can be assigned to a guest with VFIO, that device must be bound to the vfio-pci driver rather than to the device's normal host driver. The vfio-pci driver provides APIs that permit QEMU to perform all the necessary operations to make the device accessible to the guest. In the past vfio-pci was the only driver that supplied these APIs, but there are now vendor/device-specific "VFIO variant" drivers that provide the basic vfio-pci driver functionality/API while adding support for device-specific operations (for example these device-specific drivers may support live migration of certain devices). All that is needed to make this functionality available is to bind the vendor-specific "VFIO variant" driver to the device (rather than the generic vfio-pci driver, which will continue to work, just without the extra functionality). But until now libvirt has required that all PCI devices being assigned to a guest with VFIO specifically have the "vfio-pci" driver bound to the device. So even if the user manually binds a shiny new vendor-specific VFIO variant driver to the device (and puts "managed='no'" in the config to prevent libvirt from changing the binding), libvirt will just fail during startup of the guest (or during hotplug) because the driver bound to the device isn't exactly "vfio-pci". Beginning with kernel 6.1, it's possible to determine from the sysfs directory for a device whether the currently-bound driver is the vfio-pci driver or a VFIO variant - the device directory will have a subdirectory called "vfio-dev". We can use that to appropriately widen the list of drivers that libvirt will allow for VFIO device assignment. This patch doesn't remove the explicit check for the exact "vfio-pci" driver (since that would cause systems with pre-6.1 kernels to behave incorrectly), but adds an additional check for the vfio-dev directory, so that any VFIO variant driver is acceptable for libvirt to continue setting up for VFIO device assignment. Signed-off-by: Laine Stump <laine(a)redhat.com&gt; --- src/hypervisor/virhostdev.c | 28 +++++-------- src/libvirt_private.syms | 1 + src/util/virpci.c | 78 ++++++++++++++++++++++++++++++++++--- src/util/virpci.h | 3 ++ 4 files changed, 87 insertions(+), 23 deletions(-)