On Thu, Apr 20, 2017 at 4:07 PM, Stephen Bates <sba...@raithlin.com> wrote: >>> Yes, this makes sense I think we really just want to distinguish host >>> memory or not in terms of the dev_pagemap type. >> >>> I would like to see mutually exclusive flags for host memory (or not) and >>> persistence (or not). >>> >> >> Why persistence? It has zero meaning to the mm. > > I like the idea of having properties of the memory in one place.
We do have memory type data in the global iomem_resource tree, see IORES_DESC_PERSISTENT_MEMORY. > While mm might not use persistence today it may make use certain things that > persistence implies (like finite endurance and/or higher write latency) in > the future. A persistence flag does not convey endurance or latency information. > Also the persistence of the memory must have issues for mm security? Not for the mm, data at rest security might be a property of the device, but that's not the mm's concern. >Again not addressed today but useful in the future. Maybe, but to me "Useful for the future" == "don't add it to the kernel until that future arrives". > In addition I am not sure where else would be an appropriate place to put > something like a persistence property flag. I know the NVDIMM section of the > kernel uses things like NFIT to describe properties of the memory but we > don’t yet (to my knowledge) have something similar for IO memory. Do the IORES_DESC flags give you what you need?
