On Fri, Sep 9, 2016 at 1:55 AM, Xiao Guangrong <[email protected]> wrote: [..] >> >> Whether a persistent memory mapping requires an msync/fsync is a >> filesystem specific question. This mincore proposal is separate from >> that. Consider device-DAX for volatile memory or mincore() called on >> an anonymous memory range. In those cases persistence and filesystem >> metadata are not in the picture, but it would still be useful for >> userspace to know "is there page cache backing this mapping?" or "what >> is the TLB geometry of this mapping?". > > > I got a question about msync/fsync which is beyond the topic of this thread > :) > > Whether msync/fsync can make data persistent depends on ADR feature on > memory > controller, if it exists everything works well, otherwise, we need to have > another > interface that is why 'Flush hint table' in ACPI comes in. 'Flush hint > table' is > particularly useful for nvdimm virtualization if we use normal memory to > emulate > nvdimm with data persistent characteristic (the data will be flushed to a > persistent storage, e.g, disk). > > Does current PMEM programming model fully supports 'Flush hint table'? Is > userspace allowed to use these addresses?
If you publish flush hint addresses in the virtual NFIT the guest VM will write to them whenever a REQ_FLUSH or REQ_FUA request is sent to the virtual /dev/pmemX device. Yes, seems straightforward to take a VM exit on those events and flush simulated pmem to persistent storage.
