On Thu, Aug 14, 2025 at 07:54:12PM -0700, Nathan Chen via Devel wrote:
Implement iommufdId attribute for hostdev devices that can be used to specify associated iommufd object when launching a qemu VM.
Signed-off-by: Nathan Chen <nathanc@nvidia.com> --- docs/formatdomain.rst | 9 +++++++++ src/conf/domain_conf.c | 20 ++++++++++++++++++++ src/conf/domain_conf.h | 1 + src/conf/schemas/domaincommon.rng | 9 +++++++++ src/qemu/qemu_command.c | 14 ++++++++++++++ 5 files changed, 53 insertions(+)
diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst index 2558df18ef..e2b9be16c9 100644 --- a/docs/formatdomain.rst +++ b/docs/formatdomain.rst @@ -4581,6 +4581,7 @@ or: </source> <boot order='1'/> <rom bar='on' file='/etc/fake/boot.bin'/> + <iommufdId>iommufd0</iommufdId>
IIUC, the only place that is used is in the QEMU command line as an 'id' value. I'm sure we've discussed this before, but could you remind me - are we expecting every <hostdev> to have a separate iommufd FD, or are we expecting the same FD for all, or both/either ? ie we turn this into a simple yes/no flag ? If not, then we can probably turn this into a simple index value to express the uniqueness / sharing characteristics, without exposing the QEMU ID string concept directly. Either way, we can probably stuff this under <driver> rather than creating a new element eg <driver .... iommufd=yes|no> or <driver .... iommufdIndex="NNNN"/> depending on the answer to the previous Q>
</hostdev> </devices> ... @@ -4829,6 +4830,14 @@ or: device; if PCI ROM loading is disabled through this attribute, attempts to tweak the loading process further using the ``bar`` or ``file`` attributes will be rejected. :since:`Since 4.3.0 (QEMU and KVM only)`. +``iommufdId`` + The ``iommufdId`` element is used to specify using the iommufd interface to + propagate DMA mappings to the kernel, instead of legacy VFIO. When the + element is present, an iommufd object with its ID specified by ``iommufdId`` + will be created by the resulting qemu command. Libvirt will open the + /dev/iommu and VFIO device cdev, passing the associated file descriptor + numbers to the qemu command. + ``address`` The ``address`` element for USB devices has a ``bus`` and ``device`` attribute to specify the USB bus and device number the device appears at on
With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|