This patchset adds a new virt-pci driver to UML that allows users to
pass through host PCI devices to UML via VFIO. Currently, only MSI-X
capable devices are supported, and drivers are assumed to use MSI-X.
This driver has been tested with virtio-net-pci, virtio-blk-pci and
nvme in a QEMU virtual machine with virtual IOMMU enabled. Regression
testing for virtio_pcidev has only covered compile tests and partial
virtio probe/remove tests with a dummy vhost-user backend.
Here are some steps to try out this driver:
1. Enable IOMMU and bind PCI devices to the vfio-pci driver.
2. Launch a UML instance directly (assuming that the PCI devices to
be passed through to UML are 0000:02:00.0 and 0000:03:00.0).
$ ./linux mem=2G init=/bin/sh ubd0=$your_rootfs_image \
vfio_uml.device=0000:02:00.0 \
vfio_uml.device=0000:03:00.0
Note that, currently, it's not possible to allocate a large amount of
"physical" memory to the UML instance; otherwise, it may overlap with
IOMMU-reserved IOVA ranges (e.g. [0xfee00000, 0xfef00000)), causing
DMA mapping failures.
This patchset is based on the following patchset:
https://lore.kernel.org/all/20250306150747.2926434-1-tiwei....@antgroup.com/
v1:
- Add more details in the commit log;
RFC:
https://lore.kernel.org/all/20250310074057.3977758-1-tiwei....@antgroup.com/
Tiwei Bie (3):
um: Rewrite the sigio workaround based on epoll and tgkill
um: virt-pci: Refactor virtio_pcidev into its own module
um: Add VFIO-based virtual PCI driver
arch/um/drivers/Kconfig | 20 +-
arch/um/drivers/Makefile | 5 +-
arch/um/drivers/random.c | 2 +-
arch/um/drivers/rtc_user.c | 2 +-
arch/um/drivers/vfio_kern.c | 648 +++++++++++++++++++++++++++++
arch/um/drivers/vfio_user.c | 323 +++++++++++++++
arch/um/drivers/vfio_user.h | 44 ++
arch/um/drivers/virt-pci.c | 699 ++++++--------------------------
arch/um/drivers/virt-pci.h | 41 ++
arch/um/drivers/virtio_pcidev.c | 628 ++++++++++++++++++++++++++++
arch/um/include/shared/os.h | 2 +-
arch/um/include/shared/sigio.h | 1 -
arch/um/kernel/sigio.c | 26 --
arch/um/os-Linux/sigio.c | 330 ++-------------
14 files changed, 1866 insertions(+), 905 deletions(-)
create mode 100644 arch/um/drivers/vfio_kern.c
create mode 100644 arch/um/drivers/vfio_user.c
create mode 100644 arch/um/drivers/vfio_user.h
create mode 100644 arch/um/drivers/virt-pci.h
create mode 100644 arch/um/drivers/virtio_pcidev.c
--
2.34.1
