[libvirt PATCH v3 0/8] Support for VFIO variant drivers, Part 1

[Michal Prívozník]

On 8/21/23 21:32, Laine Stump wrote:
> A "VFIO variant" driver is a kernel driver for a device that supports
> all the APIs of the basic vfio-pci driver (which enables assigning a
> host PCI device to a QEMU guest) plus "some extra stuff" (e.g. to
> enable things like saving/restoring device state in order to support
> live migration.)
> 
> Way back last year I posted a couple attempts to support VFIO variant
> drivers; here is V2 (along with a later followup discussion from a
> couple months ago):
> 
> https://listman.redhat.com/archives/libvir-list/2022-August/233661.html
> https://listman.redhat.com/archives/libvir-list/2023-May/240108.html
> 
> The mlx5-vfio-pci driver has now been upstream for quite awhile (and
> even in the downstream Fedora 38 kernel, for example), as are the
> sysfs bits that allow us to determine whether or not a driver is a
> VFIO variant, and I've updated the patch(es) to use this.
> 
> I've also been working on auto-binding to the "best-match" VFIO
> variant driver based on comparing the device's modalias file in sysfs
> to the contents of the kernel's modules.alias file, but that isn't
> quite ready (partly code that isn't yet working, but also partly
> indecision about exactly where in the XML to put the driver name when
> it is specified; I won't take up more space here with that though).
> 
> In the meantime, there are people who want to use the mlx5-vfio-pci
> driver (and Cedric Le Goater also has written vfio-pci-igbvf and
> vfio-pci-e1000e drivers (which area very useful for testing), although
> I don't think he has posted them anywhere yet), so I would like to get
> the basic patches here merged in upstream now while I continue working
> on "Part 2".
> 
> These patches provide two improvements that make testing/using VFIO
> drivers much more convenient:
> 
> 1) The specific driver can be given in the virsh nodedev-detach
> command (or the virNodeDeviceDetachFlags() API call), e.g.:
> 
>     virsh nodedev-detach pci_0000_04_11_5 --driver vfio-pci-igbvf
> 
> 2) If the <hostdev> (or "<interface> ... <type='hostdev'/>" has
> "managed='no'", then libvirt will recognize any VFIO variant driver
> (rather than the current behavior of rejecting anything that isn't
> exactly "vfio-pci")
> 
> With these two capabilities, it's simple and straightforward to bind a
> device to a VFIO variant driver, and then start a guest that uses that
> device.
> 
> Change in V2:
> 
> * complete remake, more refactoring
> 
> * use existence of "vfio-dev" subdirectory of device directory in
>   sysfs to determine whether the currently-bound driver is a vfio
>   variant.
> 
> * support binding to a user-specified driver during nodedev-detach,
>   rather than only supporting vfio-pci.
> 
> Laine Stump (8):
>   util: use "stubDriverType" instead of just "stubDriver"
>   util: add stub driver name to virPCIDevice object
>   util: rename virPCIDeviceGetDriverPathAndName
>   util: permit existing binding to VFIO variant driver
>   util: probe stub driver from within function that binds to stub driver
>   util: honor stubDriverName when probing/binding stub driver for a
>     device
>   node_device: support binding other drivers with
>     virNodeDeviceDetachFlags()
>   qemu: turn two multiline log messages into single line
> 
>  src/hypervisor/domain_driver.c |   9 +-
>  src/hypervisor/domain_driver.h |   2 +
>  src/hypervisor/virhostdev.c    |  35 +++-----
>  src/libvirt_private.syms       |   9 +-
>  src/libxl/libxl_driver.c       |   3 +-
>  src/qemu/qemu_driver.c         |  37 ++++----
>  src/util/virnvme.c             |   2 +-
>  src/util/virpci.c              | 156 +++++++++++++++++++++++++--------
>  src/util/virpci.h              |  18 ++--
>  tests/virhostdevtest.c         |   2 +-
>  tests/virpcitest.c             |  10 +--
>  11 files changed, 185 insertions(+), 98 deletions(-)
> 

Reviewed-by: Michal Privoznik <mprivozn at redhat.com>

Michal