On Fri, Dec 08, 2023 at 11:12:15AM -0700, Alex Williamson wrote: > > > > avoided. But in that case RDMA knows the BAR memory is used only for > > > > doorbell write so this is a reasonable thing to do. > > > > > > Yeah, this is exactly what SPDK (and DPDK) does today. > > > > To be clear, I mean we did it in the kernel. > > > > When the device driver is removed we zap all the VMAs and install a > > fault handler that installs the dummy page instead of SIGBUS > > > > The application doesn't do anything, and this is how SPDK already will > > be supporting device hot unplug of the RDMA drivers. > > But I think you can only do that in the kernel because you understand > the device uses those pages for doorbells and it's not a general > purpose solution, right? > > Perhaps a variant driver could do something similar for NVMe devices > doorbell pages, but a device agnostic driver like vfio-pci would need > to SIGBUS on access or else we risk significant data integrity issues. > Thanks, Yes, basically. Might be interesting to consider having a VFIO FEATURE flag to opt into SIGBUS or dummy page, perhaps even on a VMA by VMA basis. Jason
