On Wed, 2015-10-28 at 15:21 -0600, Alex Williamson wrote: > There is really no way to safely give a user full access to a DMA > capable device without an IOMMU to protect the host system. There is > also no way to provide DMA translation, for use cases such as device > assignment to virtual machines. However, there are still those users > that want userspace drivers even under those conditions. The UIO > driver exists for this use case, but does not provide the degree of > device access and programming that VFIO has. In an effort to avoid > code duplication, this introduces a No-IOMMU mode for VFIO. > > This mode requires building VFIO with CONFIG_VFIO_NOIOMMU and enabling > the "enable_unsafe_noiommu_mode" option on the vfio driver. This > should make it very clear that this mode is not safe. Additionally, > CAP_SYS_RAWIO privileges are necessary to work with groups and > containers using this mode. Groups making use of this support are > named /dev/vfio/noiommu-$GROUP and can only make use of the special > VFIO_NOIOMMU_IOMMU for the container. Use of this mode, specifically > binding a device without a native IOMMU group to a VFIO bus driver > will taint the kernel and should therefore not be considered > supported. This patch includes no-iommu support for the vfio-pci bus > driver only. > > Signed-off-by: Alex Williamson <alex.william...@redhat.com> > --- > > This is pretty well the same as RFCv2, I've changed the pr_warn to a > dev_warn and added another, printing the pid and comm of the task when > it actually opens the device. If Stephen can port the driver code > over and prove that this actually works sometime next week, and there > aren't any objections to this code, I'll include it in a pull request > for the next merge window. MST, I dropped your ack due to the > changes, but I'll be happy to add it back if you like. Thanks, > > Alex > > drivers/vfio/Kconfig | 15 +++ > drivers/vfio/pci/vfio_pci.c | 8 +- > drivers/vfio/vfio.c | 186 > ++++++++++++++++++++++++++++++++++++++++++- > include/linux/vfio.h | 3 + > include/uapi/linux/vfio.h | 7 ++ > 5 files changed, 209 insertions(+), 10 deletions(-)
FYI, this is now in v4.4-rc1 (the slightly modified v2 version). I want to give fair warning though that while we seem to agree on this idea, it hasn't been proven with a userspace driver port. I've opted to include it in this merge window rather than delaying it until v4.5, but I really need to see a user for this before the end of the v4.4 cycle or I think we'll need to revert and revisit for v4.5 anyway. I don't really have any interest in adding and maintaining code that has no users. Please keep me informed of progress with a dpdk port. Thanks, Alex -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
