> > Dan Williams <dan.j.williams@xxxxxxxxx> writes: > > > [ adding Jeff directly since he has also been looking at > > infrastructure to track when MAP_SYNC should be disabled ] > > > > On Wed, Apr 25, 2018 at 7:21 AM, Dan Williams <dan.j.williams@xxxxxxxxx> > > wrote: > >> On Wed, Apr 25, 2018 at 4:24 AM, Pankaj Gupta <pagupta@xxxxxxxxxx> wrote: > >>> This patch adds virtio-pmem driver for KVM > >>> guest. > >> > >> Minor nit, please expand your changelog line wrapping to 72 columns. > >> > >>> > >>> Guest reads the persistent memory range > >>> information from Qemu over VIRTIO and registers > >>> it on nvdimm_bus. It also creates a nd_region > >>> object with the persistent memory range > >>> information so that existing 'nvdimm/pmem' > >>> driver can reserve this into system memory map. > >>> This way 'virtio-pmem' driver uses existing > >>> functionality of pmem driver to register persistent > >>> memory compatible for DAX capable filesystems. > >> > >> We need some additional enabling to disable MAP_SYNC for this > > enable to disable... I like it! ;-) > > >> configuration. In other words, if fsync() is required then we must > >> disable the MAP_SYNC optimization. I think this should be a struct > >> dax_device property looked up at mmap time in each MAP_SYNC capable > >> ->mmap() file operation implementation. I understand you mean we want to disable 'MAP_SYNC' optimization as we are relying on additional fsync. You mean if we add a property/flag in dax_device struct and its set, disable 'MAP_SYNC' accordingly during mmap time for corresponding filesystems? > > Ideally, qemu (seabios?) would advertise a platform capabilities > sub-table that doesn't fill in the flush bits. Could you please elaborate on this, how its related to disabling MAP_SYNC? We are not doing entire nvdimm device emulation. > > -Jeff > >
