On Thu, 6 Aug 2020 16:23:01 +0200 Pierre Morel <pmorel@xxxxxxxxxxxxx> wrote: > Hi all, > > In another series I proposed to add an architecture specific > callback to fail feature negociation on architecture need. > > In VIRTIO, we already have an entry to reject the features on the > transport basis. > > Transport is not architecture so I send a separate series in which > we fail the feature negociation inside virtio_ccw_finalize_features, > the virtio_config_ops.finalize_features for S390 CCW transport, > when the device do not propose the VIRTIO_F_IOMMU_PLATFORM. > > This solves the problem of crashing QEMU when this one is not using > a CCW device with iommu_platform=on in S390. This does work, and I'm tempted to queue this patch, but I'm wondering whether we need to give up on a cross-architecture solution already (especially keeping in mind that ccw is the only transport that is really architecture-specific). I know that we've gone through a few rounds already, and I'm not sure whether we've been there already, but: Could virtio_finalize_features() call an optional arch_has_restricted_memory_access() function and do the enforcing of IOMMU_PLATFORM? That would catch all transports, and things should work once an architecture opts in. That direction also shouldn't be a problem if virtio is a module. > > Regards, > Pierre > > Regards, > Pierre > > Pierre Morel (1): > s390: virtio-ccw: PV needs VIRTIO I/O device protection > > drivers/s390/virtio/virtio_ccw.c | 24 +++++++++++++++++++----- > 1 file changed, 19 insertions(+), 5 deletions(-) >
