Re: [Qemu-devel] [RFC PATCH 2/4] nvdimm: add functions to initialize and perform flush on back store

[Haozhong Zhang <haozhong.zhang@intel.com>]

On 04/11/17 16:22 +0800, Haozhong Zhang wrote:
> On 04/06/17 19:52 +0800, Xiao Guangrong wrote:
> > 
> > 
> > On 03/31/2017 04:41 PM, Haozhong Zhang wrote:
> > > fsync() is used to persist modifications to the back store. If the
> > > host NVDIMM is used as the back store, fsync() on Linux will trigger
> > > the write to the host flush hint address.
> > > 
> > > Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
> > > ---
> > >  hw/mem/nvdimm.c         | 22 ++++++++++++++++++++++
> > >  include/hw/mem/nvdimm.h | 13 +++++++++++++
> > >  2 files changed, 35 insertions(+)
> > > 
> > > diff --git a/hw/mem/nvdimm.c b/hw/mem/nvdimm.c
> > > index db896b0..484ab8b 100644
> > > --- a/hw/mem/nvdimm.c
> > > +++ b/hw/mem/nvdimm.c
> > > @@ -78,6 +78,26 @@ static MemoryRegion *nvdimm_get_memory_region(PCDIMMDevice *dimm)
> > >      return &nvdimm->nvdimm_mr;
> > >  }
> > > 
> > > +static void nvdimm_flush_init(NVDIMMDevice *nvdimm, MemoryRegion *hostmem_mr)
> > > +{
> > > +    if (nvdimm->flush_hint_enabled) {
> > > +        nvdimm->backend_fd = memory_region_get_fd(hostmem_mr);
> > 
> > Hmm, IIRC host-mem-file does not initalize backend_fd at all.
> 
> Oops, forgot to add this part. Thanks for remind.

Sorry, I replied too quick.

For hostmem-file, hostmem_mr->ram_block->fd is set in file_ram_alloc(),
which can be got by memory_region_get_fd() here.

Haozhong