On Wed, Feb 06, 2019 at 03:16:02PM -0500, Doug Ledford wrote: > On Wed, 2019-02-06 at 11:40 -0800, Matthew Wilcox wrote: > > On Wed, Feb 06, 2019 at 07:16:21PM +0000, Christopher Lameter wrote: > > > > > > though? If we only allow this use case then we may not have to worry about > > > long term GUP because DAX mapped files will stay in the physical location > > > regardless. > > > > ... except for truncate. And now that I think about it, there was a > > desire to support hot-unplug which also needed revoke. > > We already support hot unplug of RDMA devices. But it is extreme. How > does hot unplug deal with a program running from the device (something > that would have returned ETXTBSY)? Not hot-unplugging the RDMA device but hot-unplugging an NV-DIMM. It's straightforward to migrate text pages from one DIMM to another; you remove the PTEs from the CPU's page tables, copy the data over and pagefaults put the new PTEs in place. We don't have a way to do similar things to an RDMA device, do we?
